Re: [libvirt] [PATCH 1/2] remote: Avoid the thread race condition

From: Daniel P. Berrange <berrange(a)redhat.com&gt; https://bugzilla.redhat.com/show_bug.cgi?id=866524 Since the virConnect object is not locked wholely when doing virConenctDispose, a thread can get the lock and thus might cause the race. Detected by valgrind: ==23687== Invalid read of size 4 ==23687== at 0x38BAA091EC: pthread_mutex_lock (pthread_mutex_lock.c:61) ==23687== by 0x3FBA919E36: remoteClientCloseFunc (remote_driver.c:337) ==23687== by 0x3FBA936BF2: virNetClientCloseLocked (virnetclient.c:688) ==23687== by 0x3FBA9390D8: virNetClientIncomingEvent (virnetclient.c:1859) ==23687== by 0x3FBA851AAE: virEventPollRunOnce (event_poll.c:485) ==23687== by 0x3FBA850846: virEventRunDefaultImpl (event.c:247) ==23687== by 0x40CD61: vshEventLoop (virsh.c:2128) ==23687== by 0x3FBA8626F8: virThreadHelper (threads-pthread.c:161) ==23687== by 0x38BAA077F0: start_thread (pthread_create.c:301) ==23687== by 0x33F68E570C: clone (clone.S:115) ==23687== Address 0x4ca94e0 is 144 bytes inside a block of size 312 free'd ==23687== at 0x4A0595D: free (vg_replace_malloc.c:366) ==23687== by 0x3FBA8588B8: virFree (memory.c:309) ==23687== by 0x3FBA86AAFC: virObjectUnref (virobject.c:145) ==23687== by 0x3FBA8EA767: virConnectClose (libvirt.c:1458) ==23687== by 0x40C8B8: vshDeinit (virsh.c:2584) ==23687== by 0x41071E: main (virsh.c:3022) The above race is caused by the eventLoop thread tries to handle the net client event by calling the callback set by: virNetClientSetCloseCallback(priv->client, remoteClientCloseFunc, conn, NULL); I.E. remoteClientCloseFunc, which lock/unlock the virConnect object. This patch is to fix the bug by setting the callback to NULL when doRemoteClose. --- src/remote/remote_driver.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/src/remote/remote_driver.c b/src/remote/remote_driver.c index e5d4af3..5cc7e32 100644 --- a/src/remote/remote_driver.c +++ b/src/remote/remote_driver.c @@ -1003,6 +1003,10 @@ doRemoteClose(virConnectPtr conn, struct private_data *priv) virObjectUnref(priv->tls); priv->tls = NULL; + virNetClientSetCloseCallback(priv->client, + NULL, + NULL, + NULL); virNetClientClose(priv->client); virObjectUnref(priv->client); priv->client = NULL;