11:20 a.m.
This series fixes the crash resulting from a race condition in the connection
close callback. To observe the crash apply the first patch only. To verify that
the patchset fixes the crash please apply all but 2/6 and verify using virsh.
2/6 fixes the crash in a redundant way in case the close callback is used. In
the case it isn't 2/6 itself can't fix the issue.
For a better explanation of this problem please see the description in 6/6.
Peter Krempa (4):
DO NOT APPLY UPSTREAM: Close callback race corruption crash
reproducer.
virsh: Move cmdConnect from virsh-host.c to virsh.c
virsh: Register and unregister the close callback also in cmdConnect
rpc: Fix connection close callback race condition and memory
corruption/crash
Viktor Mihajlovski (2):
libvirt: Increase connection reference count for callbacks
virsh: Unregister the connection close notifier upon termination
src/datatypes.c | 55 ++++++++++++++++++++----
src/datatypes.h | 22 +++++++---
src/libvirt.c | 30 ++++++++-----
src/remote/remote_driver.c | 62 ++++++++++++++++-----------
src/rpc/virnetclient.c | 9 +++-
tools/virsh-host.c | 67 -----------------------------
tools/virsh.c | 102 ++++++++++++++++++++++++++++++++++++++++++---
7 files changed, 225 insertions(+), 122 deletions(-)
--
1.8.1.5
11:20 a.m.
New subject: [libvirt] [PATCHv3 1/6] DO NOT APPLY UPSTREAM: Close callback race corruption crash reproducer.
---
src/remote/remote_driver.c | 5 +++++
src/rpc/virnetclient.c | 9 ++++++++-
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/src/remote/remote_driver.c b/src/remote/remote_driver.c
index 885120e..711143a 100644
--- a/src/remote/remote_driver.c
+++ b/src/remote/remote_driver.c
@@ -1027,6 +1027,11 @@ doRemoteClose(virConnectPtr conn, struct private_data *priv)
(xdrproc_t) xdr_void, (char *) NULL) == -1)
ret = -1;
+ /* this is needed so that the remote side has the time to close the socket */
+ printf("\n\n DEBUG: Connection close called, sleeping\n\n");
+ sleep(1);
+ printf("\n\n DEBUG: Finishing close\n\n");
+
#ifdef WITH_GNUTLS
virObjectUnref(priv->tls);
priv->tls = NULL;
diff --git a/src/rpc/virnetclient.c b/src/rpc/virnetclient.c
index 010c5c3..51b80a2 100644
--- a/src/rpc/virnetclient.c
+++ b/src/rpc/virnetclient.c
@@ -674,8 +674,15 @@ virNetClientCloseLocked(virNetClientPtr client)
virKeepAliveStop(ka);
virObjectUnref(ka);
}
- if (closeCb)
+ if (closeCb) {
+ /* the callback has to delay for a while until the connection object
+ * is being freed in the original thread that closed the connection
+ * */
+ printf("\n\n DEBUG: calling the close callback\n\n");
+ sleep(2);
closeCb(client, closeReason, closeOpaque);
+ printf("\n\n DEBUG: callback returned\n\n");
+ }
virObjectLock(client);
virObjectUnref(client);
--
1.8.1.5
6:01 p.m.
New subject: [libvirt] [PATCHv3 1/6] DO NOT APPLY UPSTREAM: Close callback race corruption crash reproducer.
On 03/31/2013 10:20 AM, Peter Krempa wrote:
---
src/remote/remote_driver.c | 5 +++++
src/rpc/virnetclient.c | 9 ++++++++-
2 files changed, 13 insertions(+), 1 deletion(-)
While I agree that this must not be applied upstream, I applied it
locally and was indeed able to more reliably reproduce the problems.
Thanks; having this patch in place locally will make the rest of my
review easier.
diff --git a/src/remote/remote_driver.c b/src/remote/remote_driver.c
index 885120e..711143a 100644
--- a/src/remote/remote_driver.c
+++ b/src/remote/remote_driver.c
@@ -1027,6 +1027,11 @@ doRemoteClose(virConnectPtr conn, struct private_data *priv)
(xdrproc_t) xdr_void, (char *) NULL) == -1)
ret = -1;
+ /* this is needed so that the remote side has the time to close the socket */
+ printf("\n\n DEBUG: Connection close called, sleeping\n\n");
+ sleep(1);
+ printf("\n\n DEBUG: Finishing close\n\n");
+
#ifdef WITH_GNUTLS
virObjectUnref(priv->tls);
priv->tls = NULL;
diff --git a/src/rpc/virnetclient.c b/src/rpc/virnetclient.c
index 010c5c3..51b80a2 100644
--- a/src/rpc/virnetclient.c
+++ b/src/rpc/virnetclient.c
@@ -674,8 +674,15 @@ virNetClientCloseLocked(virNetClientPtr client)
virKeepAliveStop(ka);
virObjectUnref(ka);
}
- if (closeCb)
+ if (closeCb) {
+ /* the callback has to delay for a while until the connection object
+ * is being freed in the original thread that closed the connection
+ * */
+ printf("\n\n DEBUG: calling the close callback\n\n");
+ sleep(2);
closeCb(client, closeReason, closeOpaque);
+ printf("\n\n DEBUG: callback returned\n\n");
+ }
virObjectLock(client);
virObjectUnref(client);
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
11:20 a.m.
New subject: [libvirt] [PATCHv3 2/6] libvirt: Increase connection reference count for callbacks
From: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
By adjusting the reference count of the connection object we
prevent races between callback function and virConnectClose.
Signed-off-by: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
---
src/libvirt.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/src/libvirt.c b/src/libvirt.c
index 4b9ea75..e9aff8a 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -20186,6 +20186,8 @@ int virConnectRegisterCloseCallback(virConnectPtr conn,
return -1;
}
+ virObjectRef(conn);
+
virMutexLock(&conn->lock);
virCheckNonNullArgGoto(cb, error);
@@ -20206,6 +20208,7 @@ int virConnectRegisterCloseCallback(virConnectPtr conn,
error:
virMutexUnlock(&conn->lock);
+ virObjectUnref(conn);
virDispatchError(NULL);
return -1;
}
@@ -20255,6 +20258,8 @@ int virConnectUnregisterCloseCallback(virConnectPtr conn,
virMutexUnlock(&conn->lock);
+ virObjectUnref(conn);
+
return 0;
error:
--
1.8.1.5
5:46 p.m.
New subject: [libvirt] [PATCHv3 2/6] libvirt: Increase connection reference count for callbacks
On 03/31/2013 10:20 AM, Peter Krempa wrote:
From: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
By adjusting the reference count of the connection object we
prevent races between callback function and virConnectClose.
Signed-off-by: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
---
src/libvirt.c | 5 +++++
1 file changed, 5 insertions(+)
ACK.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
11:20 a.m.
New subject: [libvirt] [PATCHv3 3/6] virsh: Unregister the connection close notifier upon termination
From: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
Before closing the connection we unregister the close callback
to prevent a reference leak.
Further, the messages on virConnectClose != 0 are a bit more specific
now.
Signed-off-by: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
---
tools/virsh.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/tools/virsh.c b/tools/virsh.c
index 7ff12ec..d6c0e8c 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -321,9 +321,18 @@ vshReconnect(vshControl *ctl)
{
bool connected = false;
- if (ctl->conn != NULL) {
+ if (ctl->conn) {
+ int ret;
+
connected = true;
- virConnectClose(ctl->conn);
+
+ virConnectUnregisterCloseCallback(ctl->conn, vshCatchDisconnect);
+ ret = virConnectClose(ctl->conn);
+ if (ret < 0)
+ vshError(ctl, "%s", _("Failed to disconnect from the
hypervisor"));
+ else if (ret > 0)
+ vshError(ctl, "%s", _("One or more references were leaked
after "
+ "disconnect from the hypervisor"));
}
ctl->conn = virConnectOpenAuth(ctl->name,
@@ -2660,9 +2669,13 @@ vshDeinit(vshControl *ctl)
VIR_FREE(ctl->name);
if (ctl->conn) {
int ret;
- if ((ret = virConnectClose(ctl->conn)) != 0) {
- vshError(ctl, _("Failed to disconnect from the hypervisor, %d leaked
reference(s)"), ret);
- }
+ virConnectUnregisterCloseCallback(ctl->conn, vshCatchDisconnect);
+ ret = virConnectClose(ctl->conn);
+ if (ret < 0)
+ vshError(ctl, "%s", _("Failed to disconnect from the
hypervisor"));
+ else if (ret > 0)
+ vshError(ctl, "%s", _("One or more references were leaked
after "
+ "disconnect from the hypervisor"));
}
virResetLastError();
--
1.8.1.5
6:07 p.m.
New subject: [libvirt] [PATCHv3 3/6] virsh: Unregister the connection close notifier upon termination
On 03/31/2013 10:20 AM, Peter Krempa wrote:
From: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
Before closing the connection we unregister the close callback
to prevent a reference leak.
Further, the messages on virConnectClose != 0 are a bit more specific
now.
Signed-off-by: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
---
tools/virsh.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
ACK.
Thanks to patch 2/6, you could now technically close the connection
first, then unregister the callback, and the reference held by the
callback will ensure that the connection lives long enough to let that
work even after things were "closed". Most likely to happen if things
are multithreaded, where one thread is unregistering while another
thread is closing the connection. But given that earlier libvirt had
problems, we obviously don't want to advertise that "backwards" approach
to cleanup.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
11:20 a.m.
New subject: [libvirt] [PATCHv3 4/6] virsh: Move cmdConnect from virsh-host.c to virsh.c
The function is used to establish connection so it should be in the main
virsh file. This movement also enables further improvements done in next
patches.
---
tools/virsh-host.c | 67 ----------------------------------------------------
tools/virsh.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 69 insertions(+), 67 deletions(-)
diff --git a/tools/virsh-host.c b/tools/virsh-host.c
index 2d49296..a7e31da 100644
--- a/tools/virsh-host.c
+++ b/tools/virsh-host.c
@@ -68,67 +68,6 @@ cmdCapabilities(vshControl *ctl, const vshCmd *cmd ATTRIBUTE_UNUSED)
}
/*
- * "connect" command
- */
-static const vshCmdInfo info_connect[] = {
- {.name = "help",
- .data = N_("(re)connect to hypervisor")
- },
- {.name = "desc",
- .data = N_("Connect to local hypervisor. This is built-in "
- "command after shell start up.")
- },
- {.name = NULL}
-};
-
-static const vshCmdOptDef opts_connect[] = {
- {.name = "name",
- .type = VSH_OT_DATA,
- .flags = VSH_OFLAG_EMPTY_OK,
- .help = N_("hypervisor connection URI")
- },
- {.name = "readonly",
- .type = VSH_OT_BOOL,
- .help = N_("read-only connection")
- },
- {.name = NULL}
-};
-
-static bool
-cmdConnect(vshControl *ctl, const vshCmd *cmd)
-{
- bool ro = vshCommandOptBool(cmd, "readonly");
- const char *name = NULL;
-
- if (ctl->conn) {
- int ret;
- if ((ret = virConnectClose(ctl->conn)) != 0) {
- vshError(ctl, _("Failed to disconnect from the hypervisor, %d leaked
reference(s)"), ret);
- return false;
- }
- ctl->conn = NULL;
- }
-
- VIR_FREE(ctl->name);
- if (vshCommandOptStringReq(ctl, cmd, "name", &name) < 0)
- return false;
-
- ctl->name = vshStrdup(ctl, name);
-
- ctl->useGetInfo = false;
- ctl->useSnapshotOld = false;
- ctl->readonly = ro;
-
- ctl->conn = virConnectOpenAuth(ctl->name, virConnectAuthPtrDefault,
- ctl->readonly ? VIR_CONNECT_RO : 0);
-
- if (!ctl->conn)
- vshError(ctl, "%s", _("Failed to connect to the
hypervisor"));
-
- return !!ctl->conn;
-}
-
-/*
* "freecell" command
*/
static const vshCmdInfo info_freecell[] = {
@@ -912,12 +851,6 @@ const vshCmdDef hostAndHypervisorCmds[] = {
.info = info_capabilities,
.flags = 0
},
- {.name = "connect",
- .handler = cmdConnect,
- .opts = opts_connect,
- .info = info_connect,
- .flags = VSH_CMD_FLAG_NOCONNECT
- },
{.name = "freecell",
.handler = cmdFreecell,
.opts = opts_freecell,
diff --git a/tools/virsh.c b/tools/virsh.c
index d6c0e8c..a43c236 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -355,6 +355,69 @@ vshReconnect(vshControl *ctl)
ctl->useSnapshotOld = false;
}
+
+/*
+ * "connect" command
+ */
+static const vshCmdInfo info_connect[] = {
+ {.name = "help",
+ .data = N_("(re)connect to hypervisor")
+ },
+ {.name = "desc",
+ .data = N_("Connect to local hypervisor. This is built-in "
+ "command after shell start up.")
+ },
+ {.name = NULL}
+};
+
+static const vshCmdOptDef opts_connect[] = {
+ {.name = "name",
+ .type = VSH_OT_DATA,
+ .flags = VSH_OFLAG_EMPTY_OK,
+ .help = N_("hypervisor connection URI")
+ },
+ {.name = "readonly",
+ .type = VSH_OT_BOOL,
+ .help = N_("read-only connection")
+ },
+ {.name = NULL}
+};
+
+static bool
+cmdConnect(vshControl *ctl, const vshCmd *cmd)
+{
+ bool ro = vshCommandOptBool(cmd, "readonly");
+ const char *name = NULL;
+
+ if (ctl->conn) {
+ int ret;
+ if ((ret = virConnectClose(ctl->conn)) != 0) {
+ vshError(ctl, _("Failed to disconnect from the hypervisor, %d leaked
reference(s)"), ret);
+ return false;
+ }
+ ctl->conn = NULL;
+ }
+
+ VIR_FREE(ctl->name);
+ if (vshCommandOptStringReq(ctl, cmd, "name", &name) < 0)
+ return false;
+
+ ctl->name = vshStrdup(ctl, name);
+
+ ctl->useGetInfo = false;
+ ctl->useSnapshotOld = false;
+ ctl->readonly = ro;
+
+ ctl->conn = virConnectOpenAuth(ctl->name, virConnectAuthPtrDefault,
+ ctl->readonly ? VIR_CONNECT_RO : 0);
+
+ if (!ctl->conn)
+ vshError(ctl, "%s", _("Failed to connect to the
hypervisor"));
+
+ return !!ctl->conn;
+}
+
+
#ifndef WIN32
static void
vshPrintRaw(vshControl *ctl, ...)
@@ -3000,6 +3063,12 @@ vshParseArgv(vshControl *ctl, int argc, char **argv)
}
static const vshCmdDef virshCmds[] = {
+ {.name = "connect",
+ .handler = cmdConnect,
+ .opts = opts_connect,
+ .info = info_connect,
+ .flags = VSH_CMD_FLAG_NOCONNECT
+ },
{.name = "cd",
.handler = cmdCd,
.opts = opts_cd,
--
1.8.1.5
6:13 p.m.
New subject: [libvirt] [PATCHv3 4/6] virsh: Move cmdConnect from virsh-host.c to virsh.c
On 03/31/2013 10:20 AM, Peter Krempa wrote:
The function is used to establish connection so it should be in the
main
virsh file. This movement also enables further improvements done in next
patches.
---
tools/virsh-host.c | 67 ----------------------------------------------------
tools/virsh.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 69 insertions(+), 67 deletions(-)
Straightforward code motion; ACK with one nit:
@@ -3000,6 +3063,12 @@ vshParseArgv(vshControl *ctl, int argc, char
**argv)
}
static const vshCmdDef virshCmds[] = {
+ {.name = "connect",
+ .handler = cmdConnect,
+ .opts = opts_connect,
+ .info = info_connect,
+ .flags = VSH_CMD_FLAG_NOCONNECT
+ },
{.name = "cd",
This is not alphabetically sorted.
Also, your commit message might mention that 'connect' has moved from
'virsh help host' into 'virsh help virsh' (I'm okay with that move,
but
it IS worth mentioning that it was intentional).
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
11:20 a.m.
New subject: [libvirt] [PATCHv3 5/6] virsh: Register and unregister the close callback also in cmdConnect
This patch improves the error message after disconnecting from the
hypervisor and adds the close callback operations required not to leak
the callback reference.
---
tools/virsh.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/tools/virsh.c b/tools/virsh.c
index a43c236..a6e6eec 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -391,10 +391,14 @@ cmdConnect(vshControl *ctl, const vshCmd *cmd)
if (ctl->conn) {
int ret;
- if ((ret = virConnectClose(ctl->conn)) != 0) {
- vshError(ctl, _("Failed to disconnect from the hypervisor, %d leaked
reference(s)"), ret);
- return false;
- }
+
+ virConnectUnregisterCloseCallback(ctl->conn, vshCatchDisconnect);
+ ret = virConnectClose(ctl->conn);
+ if (ret < 0)
+ vshError(ctl, "%s", _("Failed to disconnect from the
hypervisor"));
+ else if (ret > 0)
+ vshError(ctl, "%s", _("One or more references were leaked
after "
+ "disconnect from the hypervisor"));
ctl->conn = NULL;
}
@@ -411,10 +415,16 @@ cmdConnect(vshControl *ctl, const vshCmd *cmd)
ctl->conn = virConnectOpenAuth(ctl->name, virConnectAuthPtrDefault,
ctl->readonly ? VIR_CONNECT_RO : 0);
- if (!ctl->conn)
+ if (!ctl->conn) {
vshError(ctl, "%s", _("Failed to connect to the
hypervisor"));
+ return false;
+ }
+
+ if (virConnectRegisterCloseCallback(ctl->conn, vshCatchDisconnect,
+ NULL, NULL) < 0)
+ vshError(ctl, "%s", _("Unable to register disconnect
callback"));
- return !!ctl->conn;
+ return true;
}
--
1.8.1.5
6:21 p.m.
New subject: [libvirt] [PATCHv3 5/6] virsh: Register and unregister the close callback also in cmdConnect
On 03/31/2013 10:20 AM, Peter Krempa wrote:
This patch improves the error message after disconnecting from the
hypervisor and adds the close callback operations required not to leak
the callback reference.
---
tools/virsh.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
ACK.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
11:20 a.m.
New subject: [libvirt] [PATCHv3 6/6] rpc: Fix connection close callback race condition and memory corruption/crash
The last Viktor's effort to fix the race and memory corruption unfortunately
wasn't complete in the case the close callback was not registered in an
connection. At that time, the trail of event's that I'll describe later could
still happend and corrupt the memory or cause a crash of the client (including
the daemon in case of a p2p migration).
Consider the following prerequisities and trail of events:
Let's have a remote connection to a hypervisor that doesn't have a close
callback registered and the client is using the event loop. The crash happens in
cooperation of 2 threads. Thread E is the event loop and thread W is the worker
that does some stuff. R denotes the remote client.
1.) W - The client finishes everything and sheds the last reference on the client
2.) W - The virObject stuff invokes virConnectDispose that invokes doRemoteClose
3.) W - the remote close method invokes the REMOTE_PROC_CLOSE RPC method.
4.) W - The thread is preempted at this point.
5.) R - The remote side recieves the close and closes the socket.
6.) E - poll() wakes up due to the closed socket and invokes the close callback
7.) E - The event loop is preempted right before remoteClientCloseFunc is called
8.) W - The worker now finishes, and frees the conn object.
9.) E - The remoteClientCloseFunc accesses the now-freed conn object in the
attempt to retrieve pointer for the real close callback.
10.) Kaboom, corrupted memory/segfault.
This patch tries to fix this by introducing a new object that survives the
freeing of the connection object. We can't increase the reference count on the
connection object itself as the connection would never be closed as the
connection is closed only when the reference count reaches zero.
The new object - virConnectCloseCallbackData - is a lockable object that keeps
the pointers to the real user registered callback and ensures that the
connection callback is either not called if the connection was already freed or
that the connection isn't freed while this is being called.
---
src/datatypes.c | 55 ++++++++++++++++++++++++++++++++++++--------
src/datatypes.h | 22 ++++++++++++++----
src/libvirt.c | 29 ++++++++++++-----------
src/remote/remote_driver.c | 57 +++++++++++++++++++++++++++-------------------
4 files changed, 112 insertions(+), 51 deletions(-)
diff --git a/src/datatypes.c b/src/datatypes.c
index b04e100..b21daac 100644
--- a/src/datatypes.c
+++ b/src/datatypes.c
@@ -37,6 +37,7 @@
virClassPtr virConnectClass;
+virClassPtr virConnectCloseCallbackDataClass;
virClassPtr virDomainClass;
virClassPtr virDomainSnapshotClass;
virClassPtr virInterfaceClass;
@@ -49,6 +50,7 @@ virClassPtr virStorageVolClass;
virClassPtr virStoragePoolClass;
static void virConnectDispose(void *obj);
+static void virConnectCloseCallbackDataDispose(void *obj);
static void virDomainDispose(void *obj);
static void virDomainSnapshotDispose(void *obj);
static void virInterfaceDispose(void *obj);
@@ -63,14 +65,19 @@ static void virStoragePoolDispose(void *obj);
static int
virDataTypesOnceInit(void)
{
-#define DECLARE_CLASS(basename) \
- if (!(basename ## Class = virClassNew(virClassForObject(), \
+#define DECLARE_CLASS_COMMON(basename, parent) \
+ if (!(basename ## Class = virClassNew(parent, \
#basename, \
sizeof(basename), \
basename ## Dispose))) \
return -1;
+#define DECLARE_CLASS(basename) \
+ DECLARE_CLASS_COMMON(basename, virClassForObject())
+#define DECLARE_CLASS_LOCKABLE(basename) \
+ DECLARE_CLASS_COMMON(basename, virClassForObjectLockable())
DECLARE_CLASS(virConnect);
+ DECLARE_CLASS_LOCKABLE(virConnectCloseCallbackData);
DECLARE_CLASS(virDomain);
DECLARE_CLASS(virDomainSnapshot);
DECLARE_CLASS(virInterface);
@@ -82,6 +89,8 @@ virDataTypesOnceInit(void)
DECLARE_CLASS(virStorageVol);
DECLARE_CLASS(virStoragePool);
+#undef DECLARE_CLASS_COMMON
+#undef DECLARE_CLASS_LOCKABLE
#undef DECLARE_CLASS
return 0;
@@ -107,12 +116,17 @@ virGetConnect(void)
if (!(ret = virObjectNew(virConnectClass)))
return NULL;
- if (virMutexInit(&ret->lock) < 0) {
- VIR_FREE(ret);
- return NULL;
- }
+ if (!(ret->closeCallback = virObjectNew(virConnectCloseCallbackDataClass)))
+ goto error;
+
+ if (virMutexInit(&ret->lock) < 0)
+ goto error;
return ret;
+
+error:
+ virObjectUnref(ret);
+ return NULL;
}
/**
@@ -146,19 +160,42 @@ virConnectDispose(void *obj)
virMutexLock(&conn->lock);
- if (conn->closeFreeCallback)
- conn->closeFreeCallback(conn->closeOpaque);
-
virResetError(&conn->err);
virURIFree(conn->uri);
+ virObjectLock(conn->closeCallback);
+ conn->closeCallback->callback = NULL;
+ virObjectUnlock(conn->closeCallback);
+
+ virObjectUnref(conn->closeCallback);
+
virMutexUnlock(&conn->lock);
virMutexDestroy(&conn->lock);
}
/**
+ * virConnectCloseCallbackDataDispose:
+ * @obj: the close callback data to release
+ *
+ * Release resources bound to the connection close callback.
+ */
+static void
+virConnectCloseCallbackDataDispose(void *obj)
+{
+ virConnectCloseCallbackDataPtr cb = obj;
+
+ virObjectLock(cb);
+
+ if (cb->freeCallback)
+ cb->freeCallback(cb->opaque);
+
+ virObjectUnlock(cb);
+}
+
+
+/**
* virGetDomain:
* @conn: the hypervisor connection
* @name: pointer to the domain name
diff --git a/src/datatypes.h b/src/datatypes.h
index a1dfc1e..e5ecf18 100644
--- a/src/datatypes.h
+++ b/src/datatypes.h
@@ -93,6 +93,22 @@ extern virClassPtr virStoragePoolClass;
# define VIR_IS_DOMAIN_SNAPSHOT(obj) \
(VIR_IS_SNAPSHOT(obj) && VIR_IS_DOMAIN((obj)->domain))
+
+typedef struct _virConnectCloseCallbackData virConnectCloseCallbackData;
+typedef virConnectCloseCallbackData *virConnectCloseCallbackDataPtr;
+
+/**
+ * Internal structure holding data related to connection close callbacks.
+ */
+struct _virConnectCloseCallbackData {
+ virObjectLockable parent;
+
+ virConnectPtr conn;
+ virConnectCloseFunc callback;
+ void *opaque;
+ virFreeCallback freeCallback;
+};
+
/**
* _virConnect:
*
@@ -142,11 +158,7 @@ struct _virConnect {
void *userData; /* the user data */
/* Per-connection close callback */
- virConnectCloseFunc closeCallback;
- void *closeOpaque;
- virFreeCallback closeFreeCallback;
- bool closeDispatch;
- unsigned closeUnregisterCount;
+ virConnectCloseCallbackDataPtr closeCallback;
};
/**
diff --git a/src/libvirt.c b/src/libvirt.c
index e9aff8a..cef9f1f 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -20189,24 +20189,27 @@ int virConnectRegisterCloseCallback(virConnectPtr conn,
virObjectRef(conn);
virMutexLock(&conn->lock);
+ virObjectLock(conn->closeCallback);
virCheckNonNullArgGoto(cb, error);
- if (conn->closeCallback) {
+ if (conn->closeCallback->callback) {
virLibConnError(VIR_ERR_OPERATION_INVALID, "%s",
_("A close callback is already registered"));
goto error;
}
- conn->closeCallback = cb;
- conn->closeOpaque = opaque;
- conn->closeFreeCallback = freecb;
+ conn->closeCallback->callback = cb;
+ conn->closeCallback->opaque = opaque;
+ conn->closeCallback->freeCallback = freecb;
+ virObjectUnlock(conn->closeCallback);
virMutexUnlock(&conn->lock);
return 0;
error:
+ virObjectUnlock(conn->closeCallback);
virMutexUnlock(&conn->lock);
virObjectUnref(conn);
virDispatchError(NULL);
@@ -20240,29 +20243,29 @@ int virConnectUnregisterCloseCallback(virConnectPtr conn,
}
virMutexLock(&conn->lock);
+ virObjectLock(conn->closeCallback);
virCheckNonNullArgGoto(cb, error);
- if (conn->closeCallback != cb) {
+ if (conn->closeCallback->callback != cb) {
virLibConnError(VIR_ERR_OPERATION_INVALID, "%s",
_("A different callback was requested"));
goto error;
}
- conn->closeCallback = NULL;
- conn->closeUnregisterCount++;
- if (!conn->closeDispatch && conn->closeFreeCallback)
- conn->closeFreeCallback(conn->closeOpaque);
- conn->closeFreeCallback = NULL;
- conn->closeOpaque = NULL;
-
- virMutexUnlock(&conn->lock);
+ conn->closeCallback->callback = NULL;
+ if (conn->closeCallback->freeCallback)
+ conn->closeCallback->freeCallback(conn->closeCallback->opaque);
+ conn->closeCallback->freeCallback = NULL;
virObjectUnref(conn);
+ virObjectUnlock(conn->closeCallback);
+ virMutexUnlock(&conn->lock);
return 0;
error:
+ virObjectUnlock(conn->closeCallback);
virMutexUnlock(&conn->lock);
virDispatchError(NULL);
return -1;
diff --git a/src/remote/remote_driver.c b/src/remote/remote_driver.c
index 711143a..200043e 100644
--- a/src/remote/remote_driver.c
+++ b/src/remote/remote_driver.c
@@ -337,32 +337,38 @@ enum virDrvOpenRemoteFlags {
VIR_DRV_OPEN_REMOTE_AUTOSTART = (1 << 2), /* Autostart a per-user daemon */
};
+static void
+remoteClientCloseFreeFunc(void *opaque)
+{
+ virConnectCloseCallbackDataPtr cbdata = opaque;
+
+ virObjectUnref(cbdata);
+}
-static void remoteClientCloseFunc(virNetClientPtr client ATTRIBUTE_UNUSED,
- int reason,
- void *opaque)
+static void
+remoteClientCloseFunc(virNetClientPtr client ATTRIBUTE_UNUSED,
+ int reason,
+ void *opaque)
{
- virConnectPtr conn = opaque;
+ virConnectCloseCallbackDataPtr cbdata = opaque;
- virMutexLock(&conn->lock);
- if (conn->closeCallback) {
- virConnectCloseFunc closeCallback = conn->closeCallback;
- void *closeOpaque = conn->closeOpaque;
- virFreeCallback closeFreeCallback = conn->closeFreeCallback;
- unsigned closeUnregisterCount = conn->closeUnregisterCount;
+ virObjectLock(cbdata);
- VIR_DEBUG("Triggering connection close callback %p reason=%d",
- conn->closeCallback, reason);
- conn->closeDispatch = true;
- virMutexUnlock(&conn->lock);
- closeCallback(conn, reason, closeOpaque);
- virMutexLock(&conn->lock);
- conn->closeDispatch = false;
- if (conn->closeUnregisterCount != closeUnregisterCount &&
- closeFreeCallback)
- closeFreeCallback(closeOpaque);
+ if (cbdata->callback) {
+ VIR_DEBUG("Triggering connection close callback %p reason=%d,
opaque=%p",
+ cbdata->callback, reason, cbdata->opaque);
+ cbdata->callback(cbdata->conn, reason, cbdata->opaque);
+
+ if (cbdata->freeCallback)
+ cbdata->freeCallback(cbdata->opaque);
+ cbdata->callback = NULL;
+ cbdata->freeCallback = NULL;
}
- virMutexUnlock(&conn->lock);
+ virObjectUnlock(cbdata);
+
+ /* free the connection reference that comes along with the callback
+ * registration */
+ virObjectUnref(cbdata->conn);
}
/* helper macro to ease extraction of arguments from the URI */
@@ -765,9 +771,11 @@ doRemoteOpen(virConnectPtr conn,
goto failed;
}
+ virObjectRef(conn->closeCallback);
+
virNetClientSetCloseCallback(priv->client,
remoteClientCloseFunc,
- conn, NULL);
+ conn->closeCallback, remoteClientCloseFreeFunc);
if (!(priv->remoteProgram = virNetClientProgramNew(REMOTE_PROGRAM,
REMOTE_PROTOCOL_VERSION,
@@ -1036,10 +1044,11 @@ doRemoteClose(virConnectPtr conn, struct private_data *priv)
virObjectUnref(priv->tls);
priv->tls = NULL;
#endif
+
virNetClientSetCloseCallback(priv->client,
NULL,
- NULL,
- NULL);
+ conn->closeCallback, remoteClientCloseFreeFunc);
+
virNetClientClose(priv->client);
virObjectUnref(priv->client);
priv->client = NULL;
--
1.8.1.5
6:44 p.m.
New subject: [libvirt] [PATCHv3 6/6] rpc: Fix connection close callback race condition and memory corruption/crash
On 03/31/2013 10:20 AM, Peter Krempa wrote:
The last Viktor's effort to fix the race and memory corruption
unfortunately
wasn't complete in the case the close callback was not registered in an
connection. At that time, the trail of event's that I'll describe later could
still happend and corrupt the memory or cause a crash of the client (including
the daemon in case of a p2p migration).
Consider the following prerequisities and trail of events:
Let's have a remote connection to a hypervisor that doesn't have a close
callback registered and the client is using the event loop. The crash happens in
cooperation of 2 threads. Thread E is the event loop and thread W is the worker
that does some stuff. R denotes the remote client.
1.) W - The client finishes everything and sheds the last reference on the client
2.) W - The virObject stuff invokes virConnectDispose that invokes doRemoteClose
3.) W - the remote close method invokes the REMOTE_PROC_CLOSE RPC method.
4.) W - The thread is preempted at this point.
5.) R - The remote side recieves the close and closes the socket.
6.) E - poll() wakes up due to the closed socket and invokes the close callback
7.) E - The event loop is preempted right before remoteClientCloseFunc is called
8.) W - The worker now finishes, and frees the conn object.
9.) E - The remoteClientCloseFunc accesses the now-freed conn object in the
attempt to retrieve pointer for the real close callback.
10.) Kaboom, corrupted memory/segfault.
With patch 1/6 alone, I think I saw exactly this scenario by doing:
# virsh migrate dom qemu+ssh://remote/system --live --p2p --verbose
where I observed this on the source side under valgrind.
[as to the patch itself, I'm still testing it, and ran out of time to
definitively say ack today, but so far I'm liking it]
DEBUG: Connection close called, sleeping
2013-04-01 23:31:06.966+0000: 8724: error : virNetSocketReadWire:1181 :
End of file while reading data: : Input/output error
DEBUG: calling the close callback
DEBUG: Finishing close
==8724== Invalid read of size 4
==8724== at 0x390A009220: pthread_mutex_lock (pthread_mutex_lock.c:50)
==8724== by 0x4E89372: virMutexLock (threads-pthread.c:85)
==8724== by 0x4F76CC0: remoteClientCloseFunc (remote_driver.c:337)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df2540 is 160 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
==8724== Invalid read of size 4
==8724== at 0x390A00924C: pthread_mutex_lock (pthread_mutex_lock.c:61)
==8724== by 0x4E89372: virMutexLock (threads-pthread.c:85)
==8724== by 0x4F76CC0: remoteClientCloseFunc (remote_driver.c:337)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df2530 is 144 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
==8724== Invalid read of size 4
==8724== at 0x390A009257: pthread_mutex_lock (pthread_mutex_lock.c:127)
==8724== by 0x4E89372: virMutexLock (threads-pthread.c:85)
==8724== by 0x4F76CC0: remoteClientCloseFunc (remote_driver.c:337)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df253c is 156 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
==8724== Invalid write of size 4
==8724== at 0x390A00925C: pthread_mutex_lock (pthread_mutex_lock.c:125)
==8724== by 0x4E89372: virMutexLock (threads-pthread.c:85)
==8724== by 0x4F76CC0: remoteClientCloseFunc (remote_driver.c:337)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df2538 is 152 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
==8724== Invalid read of size 8
==8724== at 0x4F76CC5: remoteClientCloseFunc (remote_driver.c:338)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df25b8 is 280 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
==8724== Invalid read of size 4
==8724== at 0x390A00A630: pthread_mutex_unlock
(pthread_mutex_unlock.c:37)
==8724== by 0x4E893AF: virMutexUnlock (threads-pthread.c:90)
==8724== by 0x4F76DD1: remoteClientCloseFunc (remote_driver.c:354)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df2540 is 160 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
==8724== Invalid write of size 4
==8724== at 0x390A00A645: pthread_mutex_unlock
(pthread_mutex_unlock.c:46)
==8724== by 0x4E893AF: virMutexUnlock (threads-pthread.c:90)
==8724== by 0x4F76DD1: remoteClientCloseFunc (remote_driver.c:354)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df2538 is 152 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
==8724== Invalid read of size 4
==8724== at 0x390A00A64C: pthread_mutex_unlock
(pthread_mutex_unlock.c:49)
==8724== by 0x4E893AF: virMutexUnlock (threads-pthread.c:90)
==8724== by 0x4F76DD1: remoteClientCloseFunc (remote_driver.c:354)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df253c is 156 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
==8724== Invalid read of size 4
==8724== at 0x390A00A656: pthread_mutex_unlock
(pthread_mutex_unlock.c:52)
==8724== by 0x4E893AF: virMutexUnlock (threads-pthread.c:90)
==8724== by 0x4F76DD1: remoteClientCloseFunc (remote_driver.c:354)
==8724== by 0x4FA7E12: virNetClientCloseLocked (virnetclient.c:693)
==8724== by 0x4FAAB69: virNetClientIncomingEvent (virnetclient.c:1866)
==8724== by 0x4FBFE73: virNetSocketEventHandle (virnetsocket.c:1500)
==8724== by 0x4E6E69F: virEventPollDispatchHandles (event_poll.c:485)
==8724== by 0x4E6EF38: virEventPollRunOnce (event_poll.c:632)
==8724== by 0x4E6CFD7: virEventRunDefaultImpl (event.c:247)
==8724== by 0x4FB2DEB: virNetServerRun (virnetserver.c:748)
==8724== by 0x40DC17: main (libvirtd.c:1228)
==8724== Address 0x14df2530 is 144 bytes inside a block of size 312 free'd
==8724== at 0x4A063F0: free (vg_replace_malloc.c:446)
==8724== by 0x4E7AA26: virFree (memory.c:419)
==8724== by 0x4E94D5C: virObjectUnref (virobject.c:145)
==8724== by 0x4F2EEDB: virConnectClose (libvirt.c:1458)
==8724== by 0x12A9A67E: doPeer2PeerMigrate (qemu_migration.c:2630)
==8724== by 0x12A9A8BB: qemuMigrationPerformJob (qemu_migration.c:2685)
==8724== by 0x12A9B0D4: qemuMigrationPerform (qemu_migration.c:2872)
==8724== by 0x12ADA7E0: qemuDomainMigratePerform3 (qemu_driver.c:10107)
==8724== by 0x4F3D7D0: virDomainMigratePerform3 (libvirt.c:6253)
==8724== by 0x438CD7: remoteDispatchDomainMigratePerform3 (remote.c:3593)
==8724== by 0x418A8D: remoteDispatchDomainMigratePerform3Helper
(remote_dispatch.h:3629)
==8724== by 0x4FAC16D: virNetServerProgramDispatchCall
(virnetserverprogram.c:431)
==8724==
DEBUG: callback returned
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
11:20 a.m.
New subject: [libvirt] [PATCHv3 6/6] rpc: Fix connection close callback race condition and memory corruption/crash
On 03/31/2013 10:20 AM, Peter Krempa wrote:
The last Viktor's effort to fix the race and memory corruption
unfortunately
wasn't complete in the case the close callback was not registered in an
connection. At that time, the trail of event's that I'll describe later could
still happend and corrupt the memory or cause a crash of the client (including
s/happend/happen/
the daemon in case of a p2p migration).
Consider the following prerequisities and trail of events:
Let's have a remote connection to a hypervisor that doesn't have a close
callback registered and the client is using the event loop. The crash happens in
cooperation of 2 threads. Thread E is the event loop and thread W is the worker
that does some stuff. R denotes the remote client.
1.) W - The client finishes everything and sheds the last reference on the client
2.) W - The virObject stuff invokes virConnectDispose that invokes doRemoteClose
3.) W - the remote close method invokes the REMOTE_PROC_CLOSE RPC method.
4.) W - The thread is preempted at this point.
5.) R - The remote side recieves the close and closes the socket.
s/recieves/receives/
6.) E - poll() wakes up due to the closed socket and invokes the
close callback
7.) E - The event loop is preempted right before remoteClientCloseFunc is called
8.) W - The worker now finishes, and frees the conn object.
9.) E - The remoteClientCloseFunc accesses the now-freed conn object in the
attempt to retrieve pointer for the real close callback.
10.) Kaboom, corrupted memory/segfault.
This patch tries to fix this by introducing a new object that survives the
freeing of the connection object. We can't increase the reference count on the
connection object itself as the connection would never be closed as the
s/itself as/itself or/; s/closed as/closed, as/
connection is closed only when the reference count reaches zero.
The new object - virConnectCloseCallbackData - is a lockable object that keeps
the pointers to the real user registered callback and ensures that the
connection callback is either not called if the connection was already freed or
that the connection isn't freed while this is being called.
---
src/datatypes.c | 55 ++++++++++++++++++++++++++++++++++++--------
src/datatypes.h | 22 ++++++++++++++----
src/libvirt.c | 29 ++++++++++++-----------
src/remote/remote_driver.c | 57 +++++++++++++++++++++++++++-------------------
4 files changed, 112 insertions(+), 51 deletions(-)
So far, this is just a code review. I'm also planning on testing the
patch, and will report back with results later in the day.
@@ -63,14 +65,19 @@ static void virStoragePoolDispose(void *obj);
static int
virDataTypesOnceInit(void)
{
-#define DECLARE_CLASS(basename) \
- if (!(basename ## Class = virClassNew(virClassForObject(), \
+#define DECLARE_CLASS_COMMON(basename, parent) \
+ if (!(basename ## Class = virClassNew(parent, \
#basename, \
sizeof(basename), \
basename ## Dispose))) \
return -1;
+#define DECLARE_CLASS(basename) \
+ DECLARE_CLASS_COMMON(basename, virClassForObject())
+#define DECLARE_CLASS_LOCKABLE(basename) \
+ DECLARE_CLASS_COMMON(basename, virClassForObjectLockable())
Wonder if these definitions are useful enough to rename to VIR_DECLARE_*
and move into virobject.h. But that would be a separate patch, to
adjust all clients that would benefit from it.
+++ b/src/datatypes.h
@@ -93,6 +93,22 @@ extern virClassPtr virStoragePoolClass;
# define VIR_IS_DOMAIN_SNAPSHOT(obj) \
(VIR_IS_SNAPSHOT(obj) && VIR_IS_DOMAIN((obj)->domain))
+
+typedef struct _virConnectCloseCallbackData virConnectCloseCallbackData;
+typedef virConnectCloseCallbackData *virConnectCloseCallbackDataPtr;
+
+/**
+ * Internal structure holding data related to connection close callbacks.
+ */
+struct _virConnectCloseCallbackData {
+ virObjectLockable parent;
+
+ virConnectPtr conn;
+ virConnectCloseFunc callback;
+ void *opaque;
+ virFreeCallback freeCallback;
+};
Would it make sense to move this struct definition to be local to
datatypes.c, and have all other uses of it treat it as opaque?...
+++ b/src/libvirt.c
@@ -20189,24 +20189,27 @@ int virConnectRegisterCloseCallback(virConnectPtr conn,
virObjectRef(conn);
virMutexLock(&conn->lock);
+ virObjectLock(conn->closeCallback);
virCheckNonNullArgGoto(cb, error);
- if (conn->closeCallback) {
+ if (conn->closeCallback->callback) {
...But then you would need to expose an accessor function instead of
directly accessing closeCallback->callback. Okay, probably fine as is.
+++ b/src/remote/remote_driver.c
@@ -337,32 +337,38 @@ enum virDrvOpenRemoteFlags {
VIR_DRV_OPEN_REMOTE_AUTOSTART = (1 << 2), /* Autostart a per-user daemon */
};
+static void
+remoteClientCloseFreeFunc(void *opaque)
+{
+ virConnectCloseCallbackDataPtr cbdata = opaque;
+
+ virObjectUnref(cbdata);
+}
You shouldn't need this; just use virObjectFreeCallback instead.
+remoteClientCloseFunc(virNetClientPtr client ATTRIBUTE_UNUSED,
+ int reason,
+ void *opaque)
{
- virConnectPtr conn = opaque;
+ virConnectCloseCallbackDataPtr cbdata = opaque;
- virMutexLock(&conn->lock);
- if (conn->closeCallback) {
- virConnectCloseFunc closeCallback = conn->closeCallback;
- void *closeOpaque = conn->closeOpaque;
- virFreeCallback closeFreeCallback = conn->closeFreeCallback;
- unsigned closeUnregisterCount = conn->closeUnregisterCount;
+ virObjectLock(cbdata);
- VIR_DEBUG("Triggering connection close callback %p reason=%d",
- conn->closeCallback, reason);
- conn->closeDispatch = true;
- virMutexUnlock(&conn->lock);
- closeCallback(conn, reason, closeOpaque);
- virMutexLock(&conn->lock);
- conn->closeDispatch = false;
- if (conn->closeUnregisterCount != closeUnregisterCount &&
- closeFreeCallback)
- closeFreeCallback(closeOpaque);
+ if (cbdata->callback) {
+ VIR_DEBUG("Triggering connection close callback %p reason=%d,
opaque=%p",
+ cbdata->callback, reason, cbdata->opaque);
+ cbdata->callback(cbdata->conn, reason, cbdata->opaque);
+
+ if (cbdata->freeCallback)
+ cbdata->freeCallback(cbdata->opaque);
+ cbdata->callback = NULL;
+ cbdata->freeCallback = NULL;
}
- virMutexUnlock(&conn->lock);
+ virObjectUnlock(cbdata);
+
+ /* free the connection reference that comes along with the callback
+ * registration */
+ virObjectUnref(cbdata->conn);
}
Took me a couple reads, but it looks right. The old code had to
temporarily drop connection lock while using the callback; the new code
never even grabs connection lock because all the callback data is
encapsulated in a separate object.
/* helper macro to ease extraction of arguments from the URI */
@@ -765,9 +771,11 @@ doRemoteOpen(virConnectPtr conn,
goto failed;
}
+ virObjectRef(conn->closeCallback);
+
virNetClientSetCloseCallback(priv->client,
remoteClientCloseFunc,
- conn, NULL);
+ conn->closeCallback, remoteClientCloseFreeFunc);
Here's where virObjectFreeCallback comes in handy.
On the surface, the code seems reasonable. If my testing passes, and
you fix up the typos and the unneeded helper function, then I don't mind
giving:
ACK.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
9:50 p.m.
New subject: [libvirt] [PATCHv3 6/6] rpc: Fix connection close callback race condition and memory corruption/crash
On 03/31/2013 10:20 AM, Peter Krempa wrote:
The last Viktor's effort to fix the race and memory corruption
unfortunately
wasn't complete in the case the close callback was not registered in an
connection. At that time, the trail of event's that I'll describe later could
still happend and corrupt the memory or cause a crash of the client (including
the daemon in case of a p2p migration).
The new object - virConnectCloseCallbackData - is a lockable object that keeps
the pointers to the real user registered callback and ensures that the
connection callback is either not called if the connection was already freed or
that the connection isn't freed while this is being called.
---
src/datatypes.c | 55 ++++++++++++++++++++++++++++++++++++--------
src/datatypes.h | 22 ++++++++++++++----
src/libvirt.c | 29 ++++++++++++-----------
src/remote/remote_driver.c | 57 +++++++++++++++++++++++++++-------------------
4 files changed, 112 insertions(+), 51 deletions(-)
I've (finally) completed my stress-testing, and agree that this patch is
sufficient to avoid the race (especially when patch 1/6 is also applied
to make the race more obvious).
ACK, and let's get this applied and backported to maintenance branches
as appropriate.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
3:57 a.m.
New subject: [libvirt] [PATCHv3 6/6] rpc: Fix connection close callback race condition and memory corruption/crash
On 04/05/13 04:50, Eric Blake wrote:
On 03/31/2013 10:20 AM, Peter Krempa wrote:
> The last Viktor's effort to fix the race and memory corruption unfortunately
> wasn't complete in the case the close callback was not registered in an
> connection. At that time, the trail of event's that I'll describe later
could
> still happend and corrupt the memory or cause a crash of the client (including
> the daemon in case of a p2p migration).
>
> The new object - virConnectCloseCallbackData - is a lockable object that keeps
> the pointers to the real user registered callback and ensures that the
> connection callback is either not called if the connection was already freed or
> that the connection isn't freed while this is being called.
> ---
> src/datatypes.c | 55 ++++++++++++++++++++++++++++++++++++--------
> src/datatypes.h | 22 ++++++++++++++----
> src/libvirt.c | 29 ++++++++++++-----------
> src/remote/remote_driver.c | 57 +++++++++++++++++++++++++++-------------------
> 4 files changed, 112 insertions(+), 51 deletions(-)
I've (finally) completed my stress-testing, and agree that this patch is
sufficient to avoid the race (especially when patch 1/6 is also applied
to make the race more obvious).
ACK, and let's get this applied and backported to maintenance branches
as appropriate.
Thanks I've pushed this upstream and I will post a 0.10.2 backport later.
Peter
6:55 a.m.
On 03/31/2013 06:20 PM, Peter Krempa wrote:
This series fixes the crash resulting from a race condition in the
connection
close callback. To observe the crash apply the first patch only. To verify that
the patchset fixes the crash please apply all but 2/6 and verify using virsh.
2/6 fixes the crash in a redundant way in case the close callback is used. In
the case it isn't 2/6 itself can't fix the issue.
For a better explanation of this problem please see the description in 6/6.
Peter Krempa (4):
DO NOT APPLY UPSTREAM: Close callback race corruption crash
reproducer.
virsh: Move cmdConnect from virsh-host.c to virsh.c
virsh: Register and unregister the close callback also in cmdConnect
rpc: Fix connection close callback race condition and memory
corruption/crash
Viktor Mihajlovski (2):
libvirt: Increase connection reference count for callbacks
virsh: Unregister the connection close notifier upon termination
src/datatypes.c | 55 ++++++++++++++++++++----
src/datatypes.h | 22 +++++++---
src/libvirt.c | 30 ++++++++-----
src/remote/remote_driver.c | 62 ++++++++++++++++-----------
src/rpc/virnetclient.c | 9 +++-
tools/virsh-host.c | 67 -----------------------------
tools/virsh.c | 102 ++++++++++++++++++++++++++++++++++++++++++---
7 files changed, 225 insertions(+), 122 deletions(-)
I fear we're yet not thru this. Today I had a segfault doing a migration
using virsh migrate --verbose --live $guest qemu+ssh://$host/system.
This is with Friday's git HEAD.
The migration took very long (but succeeded except for the libvirt
crash) so there still seems to be a race lingering in the object
reference counting exposed by the --verbose option (getjobinfo?).
(gdb) bt
#0 qemuDomainGetJobInfo (dom=<optimized out>, info=0x3fffaaaaa70) at
qemu/qemu_driver.c:10166
#1 0x000003fffd4bbe68 in virDomainGetJobInfo (domain=0x3ffe4002660, info=0x3fffaaaaa70)
at libvirt.c:17440
#2 0x000002aace36b528 in remoteDispatchDomainGetJobInfo (server=<optimized out>,
msg=<optimized out>, ret=0x3ffe40029d0,
args=0x3ffe40026a0, rerr=0x3fffaaaac20, client=<optimized out>) at
remote_dispatch.h:2069
#3 remoteDispatchDomainGetJobInfoHelper (server=<optimized out>,
client=<optimized out>, msg=<optimized out>,
rerr=0x3fffaaaac20, args=0x3ffe40026a0, ret=0x3ffe40029d0) at remote_dispatch.h:2045
#4 0x000003fffd500384 in virNetServerProgramDispatchCall (msg=0x2ab035dd800,
client=0x2ab035df5d0, server=0x2ab035ca370,
prog=0x2ab035cf210) at rpc/virnetserverprogram.c:439
#5 virNetServerProgramDispatch (prog=0x2ab035cf210, server=0x2ab035ca370,
client=0x2ab035df5d0, msg=0x2ab035dd800)
at rpc/virnetserverprogram.c:305
#6 0x000003fffd4fad3c in virNetServerProcessMsg (msg=<optimized out>,
prog=<optimized out>, client=<optimized out>,
srv=0x2ab035ca370) at rpc/virnetserver.c:162
#7 virNetServerHandleJob (jobOpaque=<optimized out>, opaque=0x2ab035ca370) at
rpc/virnetserver.c:183
#8 0x000003fffd42a91c in virThreadPoolWorker (opaque=opaque@entry=0x2ab035a9e60) at
util/virthreadpool.c:144
#9 0x000003fffd42a236 in virThreadHelper (data=<optimized out>) at
util/virthreadpthread.c:161
#10 0x000003fffcdee412 in start_thread () from /lib64/libpthread.so.0
#11 0x000003fffcd30056 in thread_start () from /lib64/libc.so.6
(gdb) l
10161 if (!(vm = qemuDomObjFromDomain(dom)))
10162 goto cleanup;
10163
10164 priv = vm->privateData;
10165
10166 if (virDomainObjIsActive(vm)) {
10167 if (priv->job.asyncJob && !priv->job.dump_memory_only) {
10168 memcpy(info, &priv->job.info, sizeof(*info));
10169
10170 /* Refresh elapsed time again just to ensure it
(gdb) print *vm
$1 = {parent = {parent = {magic = 3735928559, refs = 0, klass = 0xdeadbeef}, lock = {lock
= {__data = {__lock = 0,
__count = 0, __owner = 0, __nusers = 0, __kind = 0, __spins = 0, __list =
{__prev = 0x0, __next = 0x0}},
__size = '\000' <repeats 39 times>, __align = 0}}}, pid = 0, state =
{state = 0, reason = 0}, autostart = 0,
persistent = 0, updated = 0, def = 0x0, newDef = 0x0, snapshots = 0x0, current_snapshot
= 0x0, hasManagedSave = false,
privateData = 0x0, privateDataFreeFunc = 0x0, taint = 0}
I am currently blocked with other work but if anyone has a theory that
I should verify let me know...
--
Mit freundlichen Grüßen/Kind Regards
Viktor Mihajlovski
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Martina Köderitz
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294
7:06 a.m.
On 04/08/13 13:55, Viktor Mihajlovski wrote:
I fear we're yet not thru this. Today I had a segfault doing a
migration
using virsh migrate --verbose --live $guest qemu+ssh://$host/system.
This is with Friday's git HEAD.
The migration took very long (but succeeded except for the libvirt
crash) so there still seems to be a race lingering in the object
reference counting exposed by the --verbose option (getjobinfo?).
(gdb) bt
#0 qemuDomainGetJobInfo (dom=<optimized out>, info=0x3fffaaaaa70) at
qemu/qemu_driver.c:10166
#1 0x000003fffd4bbe68 in virDomainGetJobInfo (domain=0x3ffe4002660, info=0x3fffaaaaa70)
at libvirt.c:17440
#2 0x000002aace36b528 in remoteDispatchDomainGetJobInfo (server=<optimized out>,
msg=<optimized out>, ret=0x3ffe40029d0,
args=0x3ffe40026a0, rerr=0x3fffaaaac20, client=<optimized out>) at
remote_dispatch.h:2069
#3 remoteDispatchDomainGetJobInfoHelper (server=<optimized out>,
client=<optimized out>, msg=<optimized out>,
rerr=0x3fffaaaac20, args=0x3ffe40026a0, ret=0x3ffe40029d0) at
remote_dispatch.h:2045
#4 0x000003fffd500384 in virNetServerProgramDispatchCall (msg=0x2ab035dd800,
client=0x2ab035df5d0, server=0x2ab035ca370,
prog=0x2ab035cf210) at rpc/virnetserverprogram.c:439
#5 virNetServerProgramDispatch (prog=0x2ab035cf210, server=0x2ab035ca370,
client=0x2ab035df5d0, msg=0x2ab035dd800)
at rpc/virnetserverprogram.c:305
#6 0x000003fffd4fad3c in virNetServerProcessMsg (msg=<optimized out>,
prog=<optimized out>, client=<optimized out>,
srv=0x2ab035ca370) at rpc/virnetserver.c:162
#7 virNetServerHandleJob (jobOpaque=<optimized out>, opaque=0x2ab035ca370) at
rpc/virnetserver.c:183
#8 0x000003fffd42a91c in virThreadPoolWorker (opaque=opaque@entry=0x2ab035a9e60) at
util/virthreadpool.c:144
#9 0x000003fffd42a236 in virThreadHelper (data=<optimized out>) at
util/virthreadpthread.c:161
#10 0x000003fffcdee412 in start_thread () from /lib64/libpthread.so.0
#11 0x000003fffcd30056 in thread_start () from /lib64/libc.so.6
(gdb) l
10161 if (!(vm = qemuDomObjFromDomain(dom)))
10162 goto cleanup;
10163
10164 priv = vm->privateData;
10165
10166 if (virDomainObjIsActive(vm)) {
10167 if (priv->job.asyncJob && !priv->job.dump_memory_only) {
10168 memcpy(info, &priv->job.info, sizeof(*info));
10169
10170 /* Refresh elapsed time again just to ensure it
(gdb) print *vm
$1 = {parent = {parent = {magic = 3735928559, refs = 0, klass = 0xdeadbeef}, lock = {lock
= {__data = {__lock = 0,
__count = 0, __owner = 0, __nusers = 0, __kind = 0, __spins = 0, __list =
{__prev = 0x0, __next = 0x0}},
__size = '\000' <repeats 39 times>, __align = 0}}}, pid = 0, state
= {state = 0, reason = 0}, autostart = 0,
persistent = 0, updated = 0, def = 0x0, newDef = 0x0, snapshots = 0x0,
current_snapshot = 0x0, hasManagedSave = false,
privateData = 0x0, privateDataFreeFunc = 0x0, taint = 0}
I am currently blocked with other work but if anyone has a theory that
I should verify let me know...
Aiee, perhaps a race between a thread freeing a domain object (and the
private data) and another thread that happened to acquire the domain
object pointer before it was freed? Let me verify if that is possible.
Peter
7:35 a.m.
On 04/08/13 14:06, Peter Krempa wrote:
On 04/08/13 13:55, Viktor Mihajlovski wrote:
> I fear we're yet not thru this. Today I had a segfault doing a migration
> using virsh migrate --verbose --live $guest qemu+ssh://$host/system.
> This is with Friday's git HEAD.
> The migration took very long (but succeeded except for the libvirt
> crash) so there still seems to be a race lingering in the object
> reference counting exposed by the --verbose option (getjobinfo?).
>
> (gdb) bt
> #0 qemuDomainGetJobInfo (dom=<optimized out>, info=0x3fffaaaaa70) at
> qemu/qemu_driver.c:10166
> #1 0x000003fffd4bbe68 in virDomainGetJobInfo (domain=0x3ffe4002660,
> info=0x3fffaaaaa70) at libvirt.c:17440
> #2 0x000002aace36b528 in remoteDispatchDomainGetJobInfo
> (server=<optimized out>, msg=<optimized out>, ret=0x3ffe40029d0,
> args=0x3ffe40026a0, rerr=0x3fffaaaac20, client=<optimized out>)
> at remote_dispatch.h:2069
> #3 remoteDispatchDomainGetJobInfoHelper (server=<optimized out>,
> client=<optimized out>, msg=<optimized out>,
> rerr=0x3fffaaaac20, args=0x3ffe40026a0, ret=0x3ffe40029d0) at
> remote_dispatch.h:2045
> #4 0x000003fffd500384 in virNetServerProgramDispatchCall
> (msg=0x2ab035dd800, client=0x2ab035df5d0, server=0x2ab035ca370,
> prog=0x2ab035cf210) at rpc/virnetserverprogram.c:439
> #5 virNetServerProgramDispatch (prog=0x2ab035cf210,
> server=0x2ab035ca370, client=0x2ab035df5d0, msg=0x2ab035dd800)
> at rpc/virnetserverprogram.c:305
> #6 0x000003fffd4fad3c in virNetServerProcessMsg (msg=<optimized out>,
> prog=<optimized out>, client=<optimized out>,
> srv=0x2ab035ca370) at rpc/virnetserver.c:162
> #7 virNetServerHandleJob (jobOpaque=<optimized out>,
> opaque=0x2ab035ca370) at rpc/virnetserver.c:183
> #8 0x000003fffd42a91c in virThreadPoolWorker
> (opaque=opaque@entry=0x2ab035a9e60) at util/virthreadpool.c:144
> #9 0x000003fffd42a236 in virThreadHelper (data=<optimized out>) at
> util/virthreadpthread.c:161
> #10 0x000003fffcdee412 in start_thread () from /lib64/libpthread.so.0
> #11 0x000003fffcd30056 in thread_start () from /lib64/libc.so.6
>
> (gdb) l
> 10161 if (!(vm = qemuDomObjFromDomain(dom)))
> 10162 goto cleanup;
> 10163
> 10164 priv = vm->privateData;
> 10165
> 10166 if (virDomainObjIsActive(vm)) {
> 10167 if (priv->job.asyncJob && !priv->job.dump_memory_only)
{
> 10168 memcpy(info, &priv->job.info, sizeof(*info));
> 10169
> 10170 /* Refresh elapsed time again just to ensure it
>
>
> (gdb) print *vm
> $1 = {parent = {parent = {magic = 3735928559, refs = 0, klass =
> 0xdeadbeef}, lock = {lock = {__data = {__lock = 0,
> __count = 0, __owner = 0, __nusers = 0, __kind = 0, __spins
> = 0, __list = {__prev = 0x0, __next = 0x0}},
> __size = '\000' <repeats 39 times>, __align = 0}}}, pid = 0,
> state = {state = 0, reason = 0}, autostart = 0,
> persistent = 0, updated = 0, def = 0x0, newDef = 0x0, snapshots =
> 0x0, current_snapshot = 0x0, hasManagedSave = false,
> privateData = 0x0, privateDataFreeFunc = 0x0, taint = 0}
>
> I am currently blocked with other work but if anyone has a theory that
> I should verify let me know...
>
Aiee, perhaps a race between a thread freeing a domain object (and the
private data) and another thread that happened to acquire the domain
object pointer before it was freed? Let me verify if that is possible.
Ufff. The domain objects in the qemu driver don't use reference counting
to track the lifecycles. Thus it's (Theoretically) possible to acquire a
lock of a domain object in one thread while another thread happens to
free the domain object.
I have a reproducer for this issue:
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index f50a964..90896cb 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -2222,6 +2222,8 @@ void virDomainObjListRemove(virDomainObjListPtr doms,
virUUIDFormat(dom->def->uuid, uuidstr);
virObjectUnlock(dom);
+ sleep(2);
+
virObjectLock(doms);
virHashRemoveEntry(doms->objs, uuidstr);
virObjectUnlock(doms);
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 997d7c3..f1aeab7 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -2300,6 +2300,8 @@ static int qemuDomainGetInfo(virDomainPtr dom,
if (!(vm = qemuDomObjFromDomain(dom)))
goto cleanup;
+ sleep(5);
+
info->state = virDomainObjGetState(vm, NULL);
if (!virDomainObjIsActive(vm)) {
and use a bash oneliner to trigger the issue:
virsh undefine domain & sleep .1; virsh dominfo domain
The daemon crashes afterwards. I'll try to come up with a fix.
Peter
8:04 a.m.
[Re-sending, there was probably a problem and the mail didn't reach the
list apparently]
On 04/08/13 14:06, Peter Krempa wrote:
On 04/08/13 13:55, Viktor Mihajlovski wrote:
> I fear we're yet not thru this. Today I had a segfault doing a migration
> using virsh migrate --verbose --live $guest qemu+ssh://$host/system.
> This is with Friday's git HEAD.
> The migration took very long (but succeeded except for the libvirt
> crash) so there still seems to be a race lingering in the object
> reference counting exposed by the --verbose option (getjobinfo?).
>
> (gdb) bt
> #0 qemuDomainGetJobInfo (dom=<optimized out>, info=0x3fffaaaaa70) at
> qemu/qemu_driver.c:10166
> #1 0x000003fffd4bbe68 in virDomainGetJobInfo (domain=0x3ffe4002660,
> info=0x3fffaaaaa70) at libvirt.c:17440
> #2 0x000002aace36b528 in remoteDispatchDomainGetJobInfo
> (server=<optimized out>, msg=<optimized out>, ret=0x3ffe40029d0,
> args=0x3ffe40026a0, rerr=0x3fffaaaac20, client=<optimized out>)
> at remote_dispatch.h:2069
> #3 remoteDispatchDomainGetJobInfoHelper (server=<optimized out>,
> client=<optimized out>, msg=<optimized out>,
> rerr=0x3fffaaaac20, args=0x3ffe40026a0, ret=0x3ffe40029d0) at
> remote_dispatch.h:2045
> #4 0x000003fffd500384 in virNetServerProgramDispatchCall
> (msg=0x2ab035dd800, client=0x2ab035df5d0, server=0x2ab035ca370,
> prog=0x2ab035cf210) at rpc/virnetserverprogram.c:439
> #5 virNetServerProgramDispatch (prog=0x2ab035cf210,
> server=0x2ab035ca370, client=0x2ab035df5d0, msg=0x2ab035dd800)
> at rpc/virnetserverprogram.c:305
> #6 0x000003fffd4fad3c in virNetServerProcessMsg (msg=<optimized out>,
> prog=<optimized out>, client=<optimized out>,
> srv=0x2ab035ca370) at rpc/virnetserver.c:162
> #7 virNetServerHandleJob (jobOpaque=<optimized out>,
> opaque=0x2ab035ca370) at rpc/virnetserver.c:183
> #8 0x000003fffd42a91c in virThreadPoolWorker
> (opaque=opaque@entry=0x2ab035a9e60) at util/virthreadpool.c:144
> #9 0x000003fffd42a236 in virThreadHelper (data=<optimized out>) at
> util/virthreadpthread.c:161
> #10 0x000003fffcdee412 in start_thread () from /lib64/libpthread.so.0
> #11 0x000003fffcd30056 in thread_start () from /lib64/libc.so.6
>
> (gdb) l
> 10161 if (!(vm = qemuDomObjFromDomain(dom)))
> 10162 goto cleanup;
> 10163
> 10164 priv = vm->privateData;
> 10165
> 10166 if (virDomainObjIsActive(vm)) {
> 10167 if (priv->job.asyncJob &&
!priv->job.dump_memory_only) {
> 10168 memcpy(info, &priv->job.info,
sizeof(*info));
> 10169
> 10170 /* Refresh elapsed time again just to ensure it
>
>
> (gdb) print *vm
> $1 = {parent = {parent = {magic = 3735928559, refs = 0, klass =
> 0xdeadbeef}, lock = {lock = {__data = {__lock = 0,
> __count = 0, __owner = 0, __nusers = 0, __kind = 0, __spins
> = 0, __list = {__prev = 0x0, __next = 0x0}},
> __size = '\000' <repeats 39 times>, __align = 0}}}, pid = 0,
> state = {state = 0, reason = 0}, autostart = 0,
> persistent = 0, updated = 0, def = 0x0, newDef = 0x0, snapshots =
> 0x0, current_snapshot = 0x0, hasManagedSave = false,
> privateData = 0x0, privateDataFreeFunc = 0x0, taint = 0}
>
> I am currently blocked with other work but if anyone has a theory that
> I should verify let me know...
>
Aiee, perhaps a race between a thread freeing a domain object (and the
private data) and another thread that happened to acquire the domain
object pointer before it was freed? Let me verify if that is possible.
Ufff. The domain objects in the qemu driver don't use reference counting
to track the lifecycles. Thus it's (Theoretically) possible to acquire a
lock of a domain object in one thread while another thread happens to
free the domain object.
I have a reproducer for this issue:
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index f50a964..90896cb 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -2222,6 +2222,8 @@ void virDomainObjListRemove(virDomainObjListPtr doms,
virUUIDFormat(dom->def->uuid, uuidstr);
virObjectUnlock(dom);
+ sleep(2);
+
virObjectLock(doms);
virHashRemoveEntry(doms->objs, uuidstr);
virObjectUnlock(doms);
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 997d7c3..f1aeab7 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -2300,6 +2300,8 @@ static int qemuDomainGetInfo(virDomainPtr dom,
if (!(vm = qemuDomObjFromDomain(dom)))
goto cleanup;
+ sleep(5);
+
info->state = virDomainObjGetState(vm, NULL);
if (!virDomainObjIsActive(vm)) {
and use a bash oneliner to trigger the issue:
virsh undefine domain & sleep .1; virsh dominfo domain
The daemon crashes afterwards. I'll try to come up with a fix.
Peter
9:27 p.m.
On 04/08/2013 07:04 AM, Peter Krempa wrote:
> Aiee, perhaps a race between a thread freeing a domain object
(and the
> private data) and another thread that happened to acquire the domain
> object pointer before it was freed? Let me verify if that is possible.
Ufff. The domain objects in the qemu driver don't use reference counting
to track the lifecycles. Thus it's (Theoretically) possible to acquire a
lock of a domain object in one thread while another thread happens to
free the domain object.
I have a reproducer for this issue:
Thanks; I can confirm under valgrind that we have a use after free, with
all sorts of nasty heap corruption potential, after instrumenting my
source a bit more:
diff --git i/src/conf/domain_conf.c w/src/conf/domain_conf.c
index 03e5740..0572822 100644
--- i/src/conf/domain_conf.c
+++ w/src/conf/domain_conf.c
@@ -2240,7 +2240,11 @@ void virDomainObjListRemove(virDomainObjListPtr doms,
virUUIDFormat(dom->def->uuid, uuidstr);
virObjectUnlock(dom);
+ printf(" DEBUG: about to remove dom %s from list\n", uuidstr);
+ sleep(2);
+
virObjectLock(doms);
+ printf(" DEBUG: locked, removing dom %s from list\n", uuidstr);
virHashRemoveEntry(doms->objs, uuidstr);
virObjectUnlock(doms);
}
diff --git i/src/qemu/qemu_driver.c w/src/qemu/qemu_driver.c
index 2c0d7d1..98a49e9 100644
--- i/src/qemu/qemu_driver.c
+++ w/src/qemu/qemu_driver.c
@@ -2297,9 +2297,15 @@ static int qemuDomainGetInfo(virDomainPtr dom,
int err;
unsigned long long balloon;
+ char uuidstr[VIR_UUID_STRING_BUFLEN];
if (!(vm = qemuDomObjFromDomain(dom)))
goto cleanup;
+ virUUIDFormat(dom->uuid, uuidstr);
+ printf(" DEBUG: about to look up info on %s\n", uuidstr);
+ sleep(5);
+ printf(" DEBUG: looking up info on %s\n", uuidstr);
+
info->state = virDomainObjGetState(vm, NULL);
if (!virDomainObjIsActive(vm)) {
and use a bash oneliner to trigger the issue:
virsh undefine domain & sleep .1; virsh dominfo domain
valgrind shows the culprit:
DEBUG: about to remove dom 51c6fc83-65a4-e627-b698-042b00145202 from list
DEBUG: about to look up info on 51c6fc83-65a4-e627-b698-042b00145202
DEBUG: locked, removing dom 51c6fc83-65a4-e627-b698-042b00145202 from list
DEBUG: looking up info on 51c6fc83-65a4-e627-b698-042b00145202
==10033== Thread 6:
==10033== Invalid read of size 4
==10033== at 0x50FF3BB: virDomainObjGetState (domain_conf.c:16264)
==10033== by 0x1B044EF0: qemuDomainGetInfo (qemu_driver.c:2309)
==10033== by 0x515A08C: virDomainGetInfo (libvirt.c:4240)
==10033== by 0x1243CC: remoteDispatchDomainGetInfo
(remote_dispatch.h:1987)
==10033== by 0x1242B1: remoteDispatchDomainGetInfoHelper
(remote_dispatch.h:1963)
==10033== by 0x51D2EE9: virNetServerProgramDispatchCall
(virnetserverprogram.c:439)
==10033== by 0x51D2A60: virNetServerProgramDispatch
(virnetserverprogram.c:305)
==10033== by 0x51D922C: virNetServerProcessMsg (virnetserver.c:162)
==10033== by 0x51D931B: virNetServerHandleJob (virnetserver.c:183)
==10033== by 0x50B97FD: virThreadPoolWorker (virthreadpool.c:144)
==10033== by 0x50B91CE: virThreadHelper (virthreadpthread.c:161)
==10033== by 0x7CAA850: start_thread (pthread_create.c:301)
==10033== Address 0x1daf3a1c is 60 bytes inside a block of size 136 free'd
==10033== at 0x4A063F0: free (vg_replace_malloc.c:446)
==10033== by 0x506C0BD: virFree (viralloc.c:443)
==10033== by 0x50A7366: virObjectUnref (virobject.c:272)
==10033== by 0x50D1112: virDomainObjListDataFree (domain_conf.c:891)
==10033== by 0x5088F3F: virHashRemoveEntry (virhash.c:468)
==10033== by 0x50D48CA: virDomainObjListRemove (domain_conf.c:2248)
==10033== by 0x1AFF1A4A: qemuDomainRemoveInactive (qemu_domain.c:1864)
==10033== by 0x1B04ED30: qemuDomainUndefineFlags (qemu_driver.c:5704)
==10033== by 0x5166490: virDomainUndefineFlags (libvirt.c:8214)
==10033== by 0x131732: remoteDispatchDomainUndefineFlags
(remote_dispatch.h:7066)
==10033== by 0x13161F: remoteDispatchDomainUndefineFlagsHelper
(remote_dispatch.h:7044)
==10033== by 0x51D2EE9: virNetServerProgramDispatchCall
(virnetserverprogram.c:439)
Once again, I'm trying to ascertain how far back this issue appears.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
10:43 p.m.
On 04/08/2013 08:27 PM, Eric Blake wrote:
On 04/08/2013 07:04 AM, Peter Krempa wrote:
>> Aiee, perhaps a race between a thread freeing a domain object (and the
>> private data) and another thread that happened to acquire the domain
>> object pointer before it was freed? Let me verify if that is possible.
>
> Ufff. The domain objects in the qemu driver don't use reference counting
> to track the lifecycles. Thus it's (Theoretically) possible to acquire a
> lock of a domain object in one thread while another thread happens to
> free the domain object.
>
> I have a reproducer for this issue:
Thanks; I can confirm under valgrind that we have a use after free, with
all sorts of nasty heap corruption potential, after instrumenting my
source a bit more:
Once again, I'm trying to ascertain how far back this issue appears.
This time, it appears the problem is more recent. I initially suspected
commit d1c7b00b (Feb 2013, v1.0.3), since that rearranged the locks
inside virDomainObjListRemove, but even after instrumenting that
function, I was unable to get a crash; instead, I got the expected
lookup failure:
# virsh undefine fedora-local& sleep .1; virsh dominfo fedora-local
[1] 25898
Domain fedora-local has been undefined
error: failed to get domain 'fedora-local'
error: Domain not found: no domain with matching name 'fedora-local'
[1]+ Done virsh undefine fedora-local
It's too late for me now to search any more tonight, but on the bright
side, that narrows down the search, and we have at most two releases
affected (rather than all the way back to 0.10.0 on the race that
originally spawned this thread).
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
12:24 p.m.
On 04/08/2013 09:43 PM, Eric Blake wrote:
> Thanks; I can confirm under valgrind that we have a use after
free, with
> all sorts of nasty heap corruption potential, after instrumenting my
> source a bit more:
>
>
> Once again, I'm trying to ascertain how far back this issue appears.
This time, it appears the problem is more recent. I initially suspected
commit d1c7b00b (Feb 2013, v1.0.3), since that rearranged the locks
inside virDomainObjListRemove, but even after instrumenting that
function, I was unable to get a crash; instead, I got the expected
lookup failure:
# virsh undefine fedora-local& sleep .1; virsh dominfo fedora-local
[1] 25898
Domain fedora-local has been undefined
error: failed to get domain 'fedora-local'
error: Domain not found: no domain with matching name 'fedora-local'
[1]+ Done virsh undefine fedora-local
It's too late for me now to search any more tonight, but on the bright
side, that narrows down the search, and we have at most two releases
affected (rather than all the way back to 0.10.0 on the race that
originally spawned this thread).
My 'git bisect' is complete. Commit d1c7b00b introduced the bug, but
the bug was latent until commit a9e97e0 removed qemuDriverLock.
Furthermore, applying danpb's/Peter's fix [1] on top of a9e97e0
(basically fixing the latent bug of d1c7b00b) once again avoids the crash.
[1] https://www.redhat.com/archives/libvir-list/2013-April/msg00706.html
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
3:42 p.m.
On 03/31/2013 10:20 AM, Peter Krempa wrote:
This series fixes the crash resulting from a race condition in the
connection
close callback. To observe the crash apply the first patch only. To verify that
the patchset fixes the crash please apply all but 2/6 and verify using virsh.
2/6 fixes the crash in a redundant way in case the close callback is used. In
the case it isn't 2/6 itself can't fix the issue.
For a better explanation of this problem please see the description in 6/6.
Peter Krempa (4):
DO NOT APPLY UPSTREAM: Close callback race corruption crash
reproducer.
For the record, I'm currently trying to investigate where this race was
first introduced, to make it easier to state how far back this series
must be backported...
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
5:08 p.m.
On 04/08/2013 02:42 PM, Eric Blake wrote:
On 03/31/2013 10:20 AM, Peter Krempa wrote:
> This series fixes the crash resulting from a race condition in the connection
> close callback. To observe the crash apply the first patch only. To verify that
> the patchset fixes the crash please apply all but 2/6 and verify using virsh.
> 2/6 fixes the crash in a redundant way in case the close callback is used. In
> the case it isn't 2/6 itself can't fix the issue.
>
> For a better explanation of this problem please see the description in 6/6.
>
> Peter Krempa (4):
> DO NOT APPLY UPSTREAM: Close callback race corruption crash
> reproducer.
For the record, I'm currently trying to investigate where this race was
first introduced, to make it easier to state how far back this series
must be backported...
Looks like it has been present since close connection callbacks were
first added around commit b1029b6f, Jul 2012 (version 0.10.0). I just
confirmed that adding patch 1/6 on top of 0.10.0 reliably caused the
same valgrind detection of use-after-free. v0.9.13 is immune because it
predates close callbacks.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
4293
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Viktor Mihajlovski