From f47b91148a0aa22bfafab4e8a5966205cd8c1f47 Mon Sep 17 00:00:00 2001
From: Maxim Nestratov <mnestratov@virtuozzo.com>
Date: Mon, 6 Jun 2016 17:42:16 +0300
Subject: [PATCH] util: fix crash in virClassIsDerivedFrom for CloseCallbacks
 objects

There is a possibility that qemu driver frees by unreferencing its
closeCallbacks pointer as it has the only reference to the object,
while in fact not all users of CloseCallbacks called thier
virCloseCallbacksUnset.

Backtrace is the following:
Thread #1:
0  in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
1  in virCondWait (c=<optimized out>, m=<optimized out>)
    at util/virthread.c:154
2  in virThreadPoolFree (pool=0x7f0810110b50)
    at util/virthreadpool.c:266
3  in qemuStateCleanup () at qemu/qemu_driver.c:1116
4  in virStateCleanup () at libvirt.c:808
5  in main (argc=<optimized out>, argv=<optimized out>)
    at libvirtd.c:1660

Thread #2:
0  in virClassIsDerivedFrom (klass=0xdeadbeef, parent=0x7f0837c694d0) at util/virobject.c:169
1  in virObjectIsClass (anyobj=anyobj@entry=0x7f08101d4760, klass=<optimized out>) at util/virobject.c:365
2  in virObjectLock (anyobj=0x7f08101d4760) at util/virobject.c:317
3  in virCloseCallbacksUnset (closeCallbacks=0x7f08101d4760, vm=vm@entry=0x7f08101d47b0, cb=cb@entry=0x7f081d078fc0 <qemuProcessAutoDestroy>) at util/virclosecallbacks.c:163
4  in qemuProcessAutoDestroyRemove (driver=driver@entry=0x7f081018be50, vm=vm@entry=0x7f08101d47b0) at qemu/qemu_process.c:6368
5  in qemuProcessStop (driver=driver@entry=0x7f081018be50, vm=vm@entry=0x7f08101d47b0, reason=reason@entry=VIR_DOMAIN_SHUTOFF_SHUTDOWN, asyncJob=asyncJob@entry=QEMU_ASYNC_JOB_NONE, flags=flags@entry=0) at qemu/qemu_process.c:5854
6  in processMonitorEOFEvent (vm=0x7f08101d47b0, driver=0x7f081018be50) at qemu/qemu_driver.c:4585
7  qemuProcessEventHandler (data=<optimized out>, opaque=0x7f081018be50) at qemu/qemu_driver.c:4629
8  in virThreadPoolWorker (opaque=opaque@entry=0x7f0837c4f820) at util/virthreadpool.c:145
9  in virThreadHelper (data=<optimized out>) at util/virthread.c:206
10 in start_thread () from /lib64/libpthread.so.0

Let's reference CloseCallbacks object in virCloseCallbacksSet and
unreference in virCloseCallbacksUnset.

Signed-off-by: Maxim Nestratov <mnestratov@virtuozzo.com>
---
 src/util/virclosecallbacks.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/util/virclosecallbacks.c b/src/util/virclosecallbacks.c
index 82d40717a3..891a92b10d 100644
--- a/src/util/virclosecallbacks.c
+++ b/src/util/virclosecallbacks.c
@@ -141,6 +141,7 @@ virCloseCallbacksSet(virCloseCallbacksPtr closeCallbacks,
         virObjectRef(vm);
     }
 
+    virObjectRef(closeCallbacks);
     ret = 0;
  cleanup:
     virObjectUnlock(closeCallbacks);
@@ -180,6 +181,8 @@ virCloseCallbacksUnset(virCloseCallbacksPtr closeCallbacks,
     ret = 0;
  cleanup:
     virObjectUnlock(closeCallbacks);
+    if (!ret)
+        virObjectUnref(closeCallbacks);
     return ret;
 }
 
-- 
2.47.2