6:18 a.m.
This happens because of the switch to glib whose method g_malloc0 actually
correctly returns NULL on size 0 which doesn't make sense to do. The outcome of
that is that because virAllocN always returns 0, the dispatch code never fails
allocation and passes the NULL pointer to the server-side public API which
actually checks that and fails.
https://bugzilla.redhat.com/show_bug.cgi?id=1772842
Erik Skultety (3):
rpc: gendispatch: Fix a couple of places adding trailing spaces
rpc: gendispatch: Add a check for zero size client-side buffers
libvirt-domain: virConnectListDomains: Return 0 on zero-size buffer
src/libvirt-domain.c | 3 +++
src/rpc/gendispatch.pl | 12 ++++++++++--
2 files changed, 13 insertions(+), 2 deletions(-)
--
2.23.0
6:18 a.m.
New subject: [libvirt] [PATCH 1/3] rpc: gendispatch: Fix a couple of places adding trailing spaces
Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
---
src/rpc/gendispatch.pl | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/rpc/gendispatch.pl b/src/rpc/gendispatch.pl
index 7c868191d1..8656c8f205 100755
--- a/src/rpc/gendispatch.pl
+++ b/src/rpc/gendispatch.pl
@@ -1062,7 +1062,7 @@ elsif ($mode eq "server") {
print "\n";
print " $conn_type $conn_var = $conn_method(client);\n";
- print " if (!$conn_var) \n";
+ print " if (!$conn_var)\n";
print " goto cleanup;\n";
print "\n";
@@ -1144,7 +1144,7 @@ elsif ($mode eq "server") {
print "\n";
} else {
if ($modern_ret_as_list) {
- print " if ((nresults = \n";
+ print " if ((nresults =\n";
my $indln = " $prefix$call->{ProcName}(";
print $indln;
print join(",\n" . ' ' x (length $indln), @args_list);
--
2.23.0
6:18 a.m.
New subject: [libvirt] [PATCH 2/3] rpc: gendispatch: Add a check for zero size client-side buffers
After libvirt switched to GLib, we also started to use glib allocation
primitives as of commit e85e34f3. Unlike malloc which is ambiguous with
regards to size == 0 (which in our case returned a unique pointer safe
to be passed to free), g_malloc0 strictly returns NULL on size == 0.
This change broke our legacy APIs which rely on the caller to
pre-allocate the target buffer to hold the results and pass the buffer
size as an argument. Since it makes very little sense to call an API
with nowhere to store the results, fix this by returning 0 directly in
such case in the RPC dispatch code - there are modern API equivalents
allocating the target buffer automatically anyway.
https://bugzilla.redhat.com/show_bug.cgi?id=1772842
Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
---
src/rpc/gendispatch.pl | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/src/rpc/gendispatch.pl b/src/rpc/gendispatch.pl
index 8656c8f205..524d31f741 100755
--- a/src/rpc/gendispatch.pl
+++ b/src/rpc/gendispatch.pl
@@ -1073,6 +1073,14 @@ elsif ($mode eq "server") {
print " goto cleanup;\n";
print " }\n";
print "\n";
+
+
+ print " if (args->$single_ret_list_max_var == 0) {\n";
+ print " ret->$single_ret_list_name.${single_ret_list_name}_len
= 0;\n";
+ print " rv = 0;\n";
+ print " goto cleanup;\n";
+ print " }\n";
+ print "\n";
}
print join("\n", @getters_list);
--
2.23.0
6:18 a.m.
New subject: [libvirt] [PATCH 3/3] libvirt-domain: virConnectListDomains: Return 0 on zero-size buffer
It doesn't make sense to pass a target buffer into an API, declaring its
size as 0 and expect some meaningful result. Since this used to work
pre-Glib era, we shouldn't end with an error, but we can return 0
for the number of domains immediately, instead of calling into the
daemon, which is exactly what the daemon would have returned anyway.
Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
---
src/libvirt-domain.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
index 02622cb2ca..0def40fdf7 100644
--- a/src/libvirt-domain.c
+++ b/src/libvirt-domain.c
@@ -62,6 +62,9 @@ virConnectListDomains(virConnectPtr conn, int *ids, int maxids)
virCheckNonNullArgGoto(ids, error);
virCheckNonNegativeArgGoto(maxids, error);
+ if (maxids == 0)
+ return 0;
+
if (conn->driver->connectListDomains) {
int ret = conn->driver->connectListDomains(conn, ids, maxids);
if (ret < 0)
--
2.23.0
7:04 a.m.
New subject: [libvirt] [PATCH 3/3] libvirt-domain: virConnectListDomains: Return 0 on zero-size buffer
On Mon, Nov 18, 2019 at 01:18:19PM +0100, Erik Skultety wrote:
It doesn't make sense to pass a target buffer into an API,
declaring its
size as 0 and expect some meaningful result. Since this used to work
pre-Glib era, we shouldn't end with an error, but we can return 0
for the number of domains immediately, instead of calling into the
daemon, which is exactly what the daemon would have returned anyway.
Passing in size as 0 is going to be normal practice, given the calling
convention of this API design.
Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
---
src/libvirt-domain.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
index 02622cb2ca..0def40fdf7 100644
--- a/src/libvirt-domain.c
+++ b/src/libvirt-domain.c
@@ -62,6 +62,9 @@ virConnectListDomains(virConnectPtr conn, int *ids, int maxids)
virCheckNonNullArgGoto(ids, error);
virCheckNonNegativeArgGoto(maxids, error);
+ if (maxids == 0)
+ return 0;
This is too late really, as we alrady checked 'ids'.
IMHO, we should only mandate a non-NULL 'ids' parameter when
maxids > 0 a few lines earlier
All the other legacy APIs share the same validation flaw so will
also need fixing.
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
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7:26 a.m.
New subject: [libvirt] [PATCH 3/3] libvirt-domain: virConnectListDomains: Return 0 on zero-size buffer
On Mon, Nov 18, 2019 at 01:04:01PM +0000, Daniel P. Berrangé wrote:
On Mon, Nov 18, 2019 at 01:18:19PM +0100, Erik Skultety wrote:
> It doesn't make sense to pass a target buffer into an API, declaring its
> size as 0 and expect some meaningful result. Since this used to work
> pre-Glib era, we shouldn't end with an error, but we can return 0
> for the number of domains immediately, instead of calling into the
> daemon, which is exactly what the daemon would have returned anyway.
Passing in size as 0 is going to be normal practice, given the calling
convention of this API design.
>
> Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
> ---
> src/libvirt-domain.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
> index 02622cb2ca..0def40fdf7 100644
> --- a/src/libvirt-domain.c
> +++ b/src/libvirt-domain.c
> @@ -62,6 +62,9 @@ virConnectListDomains(virConnectPtr conn, int *ids, int maxids)
> virCheckNonNullArgGoto(ids, error);
> virCheckNonNegativeArgGoto(maxids, error);
>
> + if (maxids == 0)
> + return 0;
This is too late really, as we alrady checked 'ids'.
Why is ^this a problem? The pointer has to be allocated prior to calling into
the API, so a failure on a NULL pointer on client-side is fine. On server side,
the issue is remediated much earlier in the RPC dispatch code.
IMHO, we should only mandate a non-NULL 'ids' parameter when
maxids > 0 a few lines earlier
All the other legacy APIs share the same validation flaw so will
also need fixing.
Right, I was too hasty, since gendispatch took care of the server side
automatically, I forgot to adjust the public APIs manually, will do :).
Erik
7:50 a.m.
New subject: [libvirt] [PATCH 3/3] libvirt-domain: virConnectListDomains: Return 0 on zero-size buffer
On Mon, Nov 18, 2019 at 02:26:31PM +0100, Erik Skultety wrote:
On Mon, Nov 18, 2019 at 01:04:01PM +0000, Daniel P. Berrangé wrote:
> On Mon, Nov 18, 2019 at 01:18:19PM +0100, Erik Skultety wrote:
> > It doesn't make sense to pass a target buffer into an API, declaring its
> > size as 0 and expect some meaningful result. Since this used to work
> > pre-Glib era, we shouldn't end with an error, but we can return 0
> > for the number of domains immediately, instead of calling into the
> > daemon, which is exactly what the daemon would have returned anyway.
>
> Passing in size as 0 is going to be normal practice, given the calling
> convention of this API design.
>
> >
> > Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
> > ---
> > src/libvirt-domain.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
> > index 02622cb2ca..0def40fdf7 100644
> > --- a/src/libvirt-domain.c
> > +++ b/src/libvirt-domain.c
> > @@ -62,6 +62,9 @@ virConnectListDomains(virConnectPtr conn, int *ids, int
maxids)
> > virCheckNonNullArgGoto(ids, error);
> > virCheckNonNegativeArgGoto(maxids, error);
> >
> > + if (maxids == 0)
> > + return 0;
>
> This is too late really, as we alrady checked 'ids'.
Why is ^this a problem? The pointer has to be allocated prior to calling into
the API, so a failure on a NULL pointer on client-side is fine. On server side,
the issue is remediated much earlier in the RPC dispatch code.
The current regression is caused server-side, but I'm saying the
problem in general is pre-existing even client side. Chances are
that people have already had to work around this when calling it
client side.
If we fix this though, we should fix it so that we aovid the
problem both client & server side.
IOW, rather than taking the approach to avoiding calling the
API when num==0, make it valid to do the call, so that our
public API's behaviour isn't dependant on whether the client's
malloc() returns NULL or not for a zero sized allocation.
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
8:20 a.m.
New subject: [libvirt] [PATCH 3/3] libvirt-domain: virConnectListDomains: Return 0 on zero-size buffer
On Mon, Nov 18, 2019 at 01:50:03PM +0000, Daniel P. Berrangé wrote:
On Mon, Nov 18, 2019 at 02:26:31PM +0100, Erik Skultety wrote:
> On Mon, Nov 18, 2019 at 01:04:01PM +0000, Daniel P. Berrangé wrote:
> > On Mon, Nov 18, 2019 at 01:18:19PM +0100, Erik Skultety wrote:
> > > It doesn't make sense to pass a target buffer into an API, declaring
its
> > > size as 0 and expect some meaningful result. Since this used to work
> > > pre-Glib era, we shouldn't end with an error, but we can return 0
> > > for the number of domains immediately, instead of calling into the
> > > daemon, which is exactly what the daemon would have returned anyway.
> >
> > Passing in size as 0 is going to be normal practice, given the calling
> > convention of this API design.
> >
> > >
> > > Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
> > > ---
> > > src/libvirt-domain.c | 3 +++
> > > 1 file changed, 3 insertions(+)
> > >
> > > diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
> > > index 02622cb2ca..0def40fdf7 100644
> > > --- a/src/libvirt-domain.c
> > > +++ b/src/libvirt-domain.c
> > > @@ -62,6 +62,9 @@ virConnectListDomains(virConnectPtr conn, int *ids, int
maxids)
> > > virCheckNonNullArgGoto(ids, error);
> > > virCheckNonNegativeArgGoto(maxids, error);
> > >
> > > + if (maxids == 0)
> > > + return 0;
> >
> > This is too late really, as we alrady checked 'ids'.
>
> Why is ^this a problem? The pointer has to be allocated prior to calling into
> the API, so a failure on a NULL pointer on client-side is fine. On server side,
> the issue is remediated much earlier in the RPC dispatch code.
The current regression is caused server-side, but I'm saying the
problem in general is pre-existing even client side. Chances are
that people have already had to work around this when calling it
client side.
If we fix this though, we should fix it so that we aovid the
problem both client & server side.
IOW, rather than taking the approach to avoiding calling the
API when num==0, make it valid to do the call, so that our
public API's behaviour isn't dependant on whether the client's
malloc() returns NULL or not for a zero sized allocation.
I could move the same check a few lines earlier above the
virCheckNonNullArgGoto check, but that doesn't go with your idea of allowing
the client to make the RPC call. Personally, I find it rather pointless to make
an RPC call if we can deterministically tell that the result is going to be 0,
effectively a NOP.
Erik
8:23 a.m.
New subject: [libvirt] [PATCH 3/3] libvirt-domain: virConnectListDomains: Return 0 on zero-size buffer
On Mon, Nov 18, 2019 at 03:20:00PM +0100, Erik Skultety wrote:
On Mon, Nov 18, 2019 at 01:50:03PM +0000, Daniel P. Berrangé wrote:
> On Mon, Nov 18, 2019 at 02:26:31PM +0100, Erik Skultety wrote:
> > On Mon, Nov 18, 2019 at 01:04:01PM +0000, Daniel P. Berrangé wrote:
> > > On Mon, Nov 18, 2019 at 01:18:19PM +0100, Erik Skultety wrote:
> > > > It doesn't make sense to pass a target buffer into an API,
declaring its
> > > > size as 0 and expect some meaningful result. Since this used to work
> > > > pre-Glib era, we shouldn't end with an error, but we can return
0
> > > > for the number of domains immediately, instead of calling into the
> > > > daemon, which is exactly what the daemon would have returned anyway.
> > >
> > > Passing in size as 0 is going to be normal practice, given the calling
> > > convention of this API design.
> > >
> > > >
> > > > Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
> > > > ---
> > > > src/libvirt-domain.c | 3 +++
> > > > 1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
> > > > index 02622cb2ca..0def40fdf7 100644
> > > > --- a/src/libvirt-domain.c
> > > > +++ b/src/libvirt-domain.c
> > > > @@ -62,6 +62,9 @@ virConnectListDomains(virConnectPtr conn, int *ids,
int maxids)
> > > > virCheckNonNullArgGoto(ids, error);
> > > > virCheckNonNegativeArgGoto(maxids, error);
> > > >
> > > > + if (maxids == 0)
> > > > + return 0;
> > >
> > > This is too late really, as we alrady checked 'ids'.
> >
> > Why is ^this a problem? The pointer has to be allocated prior to calling into
> > the API, so a failure on a NULL pointer on client-side is fine. On server
side,
> > the issue is remediated much earlier in the RPC dispatch code.
>
> The current regression is caused server-side, but I'm saying the
> problem in general is pre-existing even client side. Chances are
> that people have already had to work around this when calling it
> client side.
>
> If we fix this though, we should fix it so that we aovid the
> problem both client & server side.
>
>
> IOW, rather than taking the approach to avoiding calling the
> API when num==0, make it valid to do the call, so that our
> public API's behaviour isn't dependant on whether the client's
> malloc() returns NULL or not for a zero sized allocation.
I could move the same check a few lines earlier above the
virCheckNonNullArgGoto check, but that doesn't go with your idea of allowing
the client to make the RPC call. Personally, I find it rather pointless to make
an RPC call if we can deterministically tell that the result is going to be 0,
effectively a NOP.
Well there's access control checks performed server side. We're not going
to leak any data by not doing the call, but we will hide the access
control failure message if we bypass it. IMHO, we shouldn't be making
assumptions client side about what the server side will do.
Regards,
Daniel
--
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|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
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participants (2)
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Erik Skultety