Re: [libvirt] [PATCH] Avoid use of free'd memory in auto destroy callback

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; The autodestroy callback code has the following function called from a hash iterator qemuDriverCloseCallbackRun(void *payload, const void *name, void *opaque) { ... char *uuidstr = name ... dom = closeDef->cb(data->driver, dom, data->conn); if (dom) virObjectUnlock(dom); virHashRemoveEntry(data->driver->closeCallbacks, uuidstr); } The closeDef->cb function may well cause the current callback to be removed, if it shuts down 'dom'. As such the use of 'uuidstr' in virHashRemoveEntry is accessing free'd memory. We must make a copy of the uuid str before invoking the callback to be safe. Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- src/qemu/qemu_conf.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c index b21392e..ee48333 100644 --- a/src/qemu/qemu_conf.c +++ b/src/qemu/qemu_conf.c @@ -510,20 +510,25 @@ qemuDriverCloseCallbackRun(void *payload, { struct qemuDriverCloseCallbackData *data = opaque; qemuDriverCloseDefPtr closeDef = payload; - const char *uuidstr = name; unsigned char uuid[VIR_UUID_BUFLEN]; + char uuidstr[VIR_UUID_STRING_BUFLEN]; virDomainObjPtr dom; VIR_DEBUG("conn=%p, thisconn=%p, uuid=%s, cb=%p", - closeDef->conn, data->conn, uuidstr, closeDef->cb); + closeDef->conn, data->conn, (const char *)name, closeDef->cb); if (data->conn != closeDef->conn || !closeDef->cb) return; - if (virUUIDParse(uuidstr, uuid) < 0) { - VIR_WARN("Failed to parse %s", uuidstr); + if (virUUIDParse(name, uuid) < 0) { + VIR_WARN("Failed to parse %s", (const char *)name); return; } + /* We need to reformat uuidstr, because closeDef->cb + * might cause the current hash entry to be removed, + * which means 'name' will have been free()d + */ + virUUIDFormat(uuid, uuidstr); if (!(dom = virDomainFindByUUID(&data->driver->domains, uuid))) { VIR_DEBUG("No domain object with UUID %s", uuidstr); -- 1.8.1