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Re: [libvirt] Segfault in event-test.c example



Hi,

I think this is same the bug I reported.
https://bugzilla.redhat.com/show_bug.cgi?id=531979
And I attach patch. This patch Isn't available?

On Mon, 11 Jan 2010 23:39:47 +0000 (UTC)
pspreadborough comcast net wrote:

> 
> ----- "Matthias Bolte" <matthias bolte googlemail com> wrote:
> 
> > 2010/1/11  <pspreadborough comcast net>:
> > >
> > > ----- "Matthias Bolte" <matthias bolte googlemail com> wrote:
> > >
> > >> 2010/1/10 ?<pspreadborough comcast net>:
> > >> >
> > >> > ----- "Matthias Bolte" <matthias bolte googlemail com> wrote:
> > >> >
> > >> >> 2010/1/10 ?<pspreadborough comcast net>:
> > >> >> >
> > >> >> > Hello,
> > >> >> >
> > >> >> > I have been trying to use the domain event C code example but
> > >> >> > unfortunately it segfaults (signal 11) every time I run it:
> > >> >> >
> > >> >> > [root Spring events-c]# ./event-test
> > >> >> > myEventAddHandleFunc:221: Add handle 5 1 0xf081a0 0x8f727f8
> > >> >> > myEventAddHandleFunc:221: Add handle 7 1 0xf09990 0x8f727f8
> > >> >> > myEventAddHandleFunc:221: Add handle 8 1 0xed7940 0x8f727f8
> > >> >> > myEventAddTimeoutFunc:251: Adding Timeout -1 0xedefa0
> > 0x8f727f8
> > >> >> > myEventAddHandleFunc:221: Add handle 11 1 0xed7940 0x8f727f8
> > >> >> > myEventAddTimeoutFunc:251: Adding Timeout -1 0xedefa0
> > 0x8f727f8
> > >> >> > main:322 :: Registering domain event cbs
> > >> >> > Segmentation fault (core dumped)
> > >> >> >
> > >> >> > ?Core was generated by
> > >> >> >
> > >> >>
> > >>
> > `/root/libvirt-0.7.5/examples/domain-events/events-c/.libs/lt-event-test'.
> > >> >> > Program terminated with signal 11, Segmentation fault.
> > >> >> > [New process 21806]
> > >> >> > [New process 21822]
> > >> >> > #0? remoteDomainEventQueueFlush (timer=-1, opaque=0x8f727f8)
> > at
> > >> >> > remote/remote_driver.c:8720
> > >> >> > 8720??????? tempQueue.count = priv->domainEvents->count;
> > >> >> > (gdb) bt
> > >> >> > #0? remoteDomainEventQueueFlush (timer=-1, opaque=0x8f727f8)
> > at
> > >> >> > remote/remote_driver.c:8720
> > >> >> > #1? 0x080490d3 in main (argc=Cannot access memory at address
> > 0x1
> > >> >> > ) at event-test.c:347
> > >> >> >
> > >> >> > The stack looks corrupted so I'm doubtful that this trace if
> > of
> > >> much
> > >> >> value.
> > >> >> > I have built
> > >> >> > and installed libvirt-0.7.5 and it and it's tools seem to be
> > >> >> operating
> > >> >> > correctly.
> > >> >>
> > >> >> I tried the event-test with libvirt-0.7.5 and QEMU/Xen and both
> > >> are
> > >> >> working as expected. No segfaults.
> > >> >>
> > >> >> Could you inspect the values of priv and priv->domainEvents in
> > GDB
> > >> >> using 'p priv' to see if they are NULL and try to dereference
> > them
> > >> in
> > >> >> GDB using 'p *priv' to see if they point to valid memory areas?
> > >> >>
> > >> >> Yes the backtrace looks corrupted. If there is stack/heap
> > >> corruption
> > >> >> involved valgrind may reveal it, so try to run the event-test
> > in
> > >> >> valgrind and see if that gives any hints.
> > >> >>
> > >> >> You can also try the GIT version of libvirt. There was a
> > invalid
> > >> free
> > >> >> call (resulting in heap corruption) in the node device code
> > fixed
> > >> >> after the 0.7.5 release. But that should have no effect on the
> > >> >> event-test.
> > >> >>
> > >> >> Matthias
> > >> >
> > >> > Matthias,
> > >> >
> > >> > priv->domainEvents is NULL, here's the gdb output:
> > >>
> > >> This explains the segfault. The next question is, why is it NULL?
> > >>
> > >> > (gdb) p *priv
> > >> > $1 = {lock = {lock = {__data = {__lock = 1, __count = 0, __owner
> > =
> > >> 21806, __kind = 0, __nusers = 1, {__spins = 0, __list = {
> > >> > ? ? ? ? ? ?__next = 0x0}}}, __size =
> > >>
> > "\001\000\000\000\000\000\000\000.U\000\000\000\000\000\000\001\000\000\000\000\000\000",
> > >> > ? ? ?__align = 1}}, sock = 150469168, watch = 3, pid = 4,
> > uses_tls =
> > >> 1982791681, is_secure = 1815048801, session = 0x782f6269,
> > >>
> > >> Seeing uses_tls and is_secure being large numbers and knowing that
> > >> both are used as boolean values in the code and should have values
> > of
> > >> 0 or 1 make me think that priv points to already freed memory
> > here.
> > >>
> > >> > ?type = 0x2f646e65 <Address 0x2f646e65 out of bounds>, counter =
> > >> 1684956536, localUses = 1668248365,
> > >> > ?hostname = 0x74656b <Address 0x74656b out of bounds>, debugLog
> > =
> > >> 0x0, saslconn = 0x0, saslDecoded = 0x0, saslDecodedLength = 0,
> > >>
> > >> type and hostname are char pointers, but the seem to point into
> > >> nowhere, confirms that this is either freed memory or priv itself
> > got
> > >> overwritten due to heap corruption.
> > >>
> > >> > ?saslDecodedOffset = 0, saslEncoded = 0x0, saslEncodedLength =
> > 0,
> > >> saslEncodedOffset = 0,
> > >> > ?buffer = '\0' <repeats 68 times>,
> > >>
> > "n\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\bQ?\b????\030\034?\b\000\000\000\000?\033?\b\001\000\000\000\002\000\000\000?\033?\b\000\000\000\000\025|?\000\a",
> > >> '\0' <repeats 11 times>, "X\000?\b", '\0' <repeats 12 times>,
> > >> "\021\000\000\000\002\000\000\000P??\b\000\000\000\000\021", '\0'
> > >> <repeats 15 times>,
> > >>
> > "\021\000\000\0008\036?\b\f\000\000\000\020\000\000\000\021\000\000\000\a\000\000\000\b\000\000\000\t\000\000\000\021\000\000\000\002\000\000\000\230\034?\b\000\000\000\000A\000\000\000\003\000\000\000\001\000\000\000\001\000"...,
> > >> bufferLength = 0,
> > >> > ?bufferOffset = 0, callbackList = 0x0, domainEvents = 0x0,
> > >> eventFlushTimer = 0, domainEventDispatching = 1, wakeupSendFD = 0,
> > >> > ?wakeupReadFD = 0, waitDispatch = 0x0, streams = 0x0}
> > >> >
> > >> > I'll try a run with valgrind and post the results.
> > >> >
> > >> > Pete
> > >> >
> > >>
> > >> Could you test the Python version of this example found in
> > >> examples/domain-events/events-python/event-test.py? Does this
> > work?
> > >>
> > >> Otherwise lets see if valgrind gives any hints.
> > >>
> > >> Matthias
> > >
> > >
> > > During initialization I notice that the myEventAddHandleFunc()
> > method is
> > > called multiple times, each time with a different fd value (5,7,8
> > and 11).
> > > The way the code is written only the last fd value is recorded and
> > then
> > > used in the poll() call. Is this the intended? if so why are the
> > preceding
> > > fds ignored?
> > >
> > > myEventAddHandleFunc:223: Add handle 5 1 0xf13480 0x97b97d8
> > > myEventAddHandleFunc:223: Add handle 7 1 0xf14c70 0x97b97d8
> > > Allocating domainEvents:0x97c6b10
> > > myEventAddHandleFunc:223: Add handle 8 1 0xee2940 0x97b97d8
> > > myEventAddTimeoutFunc:260: Adding Timeout -1 0xee9fc0 0x97b97d8
> > > Allocating domainEvents:0x97c5780
> > > myEventAddHandleFunc:223: Add handle 11 1 0xee2940 0x97b97d8
> > > myEventAddTimeoutFunc:260: Adding Timeout -1 0xee9fc0 0x97b97d8
> > > main:333 :: Registering domain event cbs
> > >
> > >
> > > Regards,
> > >
> > > Pete
> > >
> > 
> > That's strange. I can't reproduce this neither. I always get exactly
> > one call to myEventAddHandleFunc:
> > 
> > myEventAddHandleFunc:221: Add handle 3 1 0x7ff116f68b00 0x1d97f00
> > myEventAddTimeoutFunc:251: Adding Timeout -1 0x7ff116f68750 0x1d97f00
> > main:322 :: Registering domain event cbs
> > myEventUpdateHandleFunc:232: Updated Handle 0 0
> > myEventUpdateHandleFunc:232: Updated Handle 0 1
> > 
> > You could try to run the event-test in GDB and set a breakpoint on
> > myEventAddHandleFunc to see where 4 additional calls to
> > myEventAddHandleFunc come from.
> > 
> > In my case I get this backtrace when setting a breakpoint on
> > myEventAddHandleFunc:
> > 
> > (gdb) bt
> > #0  myEventAddHandleFunc (fd=6, event=1, cb=0x7f1be6ec3b00
> > <remoteDomainEventFired>, opaque=0xc68f00, ff=0) at event-test.c:220
> > #1  0x00007f1be6ecbaaf in doRemoteOpen (conn=0xc68f00,
> > priv=0x7f1be7350010, auth=0x0, flags=0) at remote/remote_driver.c:893
> > #2  0x00007f1be6ece053 in remoteOpen (conn=0xc68f00, auth=0x0,
> > flags=13007744) at remote/remote_driver.c:1076
> > #3  0x00007f1be6eb155d in do_open (name=0x7fff48400968
> > "qemu:///system", auth=0x0, flags=0) at libvirt.c:1117
> > #4  0x0000000000400eb3 in main (argc=<value optimized out>,
> > argv=<value optimized out>) at event-test.c:313
> > 
> > Matthias
> 
> 
> Matthias
> 
> Here are the four stack traces, one for each time myEventAddHandleFunc() was
> called. 
> 
> #0  myEventAddHandleFunc (fd=8, event=1, cb=0x85b480 <xenStoreWatchEvent>, opaque=0x824a7d8, ff=0) at event-test.c:223
> #1  0x007ccf55 in virEventAddHandle (fd=8, events=1, cb=0x85b480 <xenStoreWatchEvent>, opaque=0x824a7d8, ff=0)
>     at util/event.c:45
> #2  0x0085b291 in xenStoreOpen (conn=0x824a7d8, auth=0x0, flags=<value optimized out>) at xen/xs_internal.c:339
> #3  0x00844287 in xenUnifiedOpen (conn=0x824a7d8, auth=0x0, flags=0) at xen/xen_driver.c:352
> #4  0x00811d05 in do_open (name=0xbf8c49d4 "xen:///", auth=0x0, flags=0) at libvirt.c:1117
> #5  0x08048e92 in main (argc=Cannot access memory at address 0x2
> ) at event-test.c:325
> (gdb) c
> Continuing.
> (gdb) b
> Note: breakpoint 1 also set at pc 0x8048bc9.
> Breakpoint 2 at 0x8048bc9: file event-test.c, line 223.
> (gdb) bt
> #0  myEventAddHandleFunc (fd=10, event=1, cb=0x85cc70 <xenInotifyEvent>, opaque=0x824a7d8, ff=0) at event-test.c:223
> #1  0x007ccf55 in virEventAddHandle (fd=10, events=1, cb=0x85cc70 <xenInotifyEvent>, opaque=0x824a7d8, ff=0) at util/event.c:45
> #2  0x0085c827 in xenInotifyOpen (conn=0x824a7d8, auth=0x0, flags=0) at xen/xen_inotify.c:460
> #3  0x008444f1 in xenUnifiedOpen (conn=0x824a7d8, auth=0x0, flags=0) at xen/xen_driver.c:391
> #4  0x00811d05 in do_open (name=0xbf8c49d4 "xen:///", auth=0x0, flags=0) at libvirt.c:1117
> #5  0x08048e92 in main (argc=Cannot access memory at address 0x1
> ) at event-test.c:325
> (gdb) c
> Continuing.
> (gdb) bt
> #0  myEventAddHandleFunc (fd=11, event=1, cb=0x82a940 <remoteDomainEventFired>, opaque=0x824a7d8, ff=0) at event-test.c:223
> #1  0x007ccf55 in virEventAddHandle (fd=11, events=1, cb=0x82a940 <remoteDomainEventFired>, opaque=0x824a7d8, ff=0)
>     at util/event.c:45
> #2  0x0082c478 in doRemoteOpen (conn=0x824a7d8, priv=0xb7534008, auth=0x0, flags=0) at remote/remote_driver.c:894
> #3  0x00830448 in remoteOpenSecondaryDriver (conn=0x824a7d8, auth=0x0, flags=0, priv=0xbf8c2668) at remote/remote_driver.c:1006
> #4  0x0083082a in remoteNetworkOpen (conn=0x824a7d8, auth=0x0, flags=0) at remote/remote_driver.c:3549
> #5  0x00811e2f in do_open (name=0xbf8c49d4 "xen:///", auth=0x0, flags=0) at libvirt.c:1137
> #6  0x08048e92 in main (argc=1, argv=0xbf8c28b4) at event-test.c:325
> (gdb) c
> Continuing.
> (gdb) bt
> #0  myEventAddHandleFunc (fd=14, event=1, cb=0x82a940 <remoteDomainEventFired>, opaque=0x824a7d8, ff=0) at event-test.c:223
> #1  0x007ccf55 in virEventAddHandle (fd=14, events=1, cb=0x82a940 <remoteDomainEventFired>, opaque=0x824a7d8, ff=0)
>     at util/event.c:45
> #2  0x0082c478 in doRemoteOpen (conn=0x824a7d8, priv=0x8258ab0, auth=0x0, flags=0) at remote/remote_driver.c:894
> #3  0x00830448 in remoteOpenSecondaryDriver (conn=0x824a7d8, auth=0x0, flags=0, priv=0xbf8c2668) at remote/remote_driver.c:1006
> #4  0x0083078a in remoteInterfaceOpen (conn=0x824a7d8, auth=0x0, flags=0) at remote/remote_driver.c:4104
> #5  0x00811f4e in do_open (name=0xbf8c49d4 "xen:///", auth=0x0, flags=0) at libvirt.c:1156
> #6  0x08048e92 in main (argc=1, argv=0xbf8c28b4) at event-test.c:325
> 
> Regards,
> 
> Pete
> 
> 
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