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Re: [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

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