From 8630f8dbacd240c1a01994b88ba5abb3a27bcdf0 Mon Sep 17 00:00:00 2001 From: Michal Privoznik Date: Thu, 3 Sep 2015 12:11:53 +0200 Subject: [PATCH] remoteClientCloseFunc: Don't mangle connection object refcount Well, in 8ad126e6 we tried to fix a memory corruption problem. However, the fix was not as good as it could be. I mean, the commit has one line more than it should. I've noticed this output just recently: # ./run valgrind --leak-check=full --show-reachable=yes ./tools/virsh domblklist gentoo ==17019== Memcheck, a memory error detector ==17019== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al. ==17019== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info ==17019== Command: /home/zippy/work/libvirt/libvirt.git/tools/.libs/virsh domblklist gentoo ==17019== Target Source ------------------------------------------------ fda /var/lib/libvirt/images/fd.img vda /var/lib/libvirt/images/gentoo.qcow2 hdc /home/zippy/tmp/install-amd64-minimal-20150402.iso ==17019== Thread 2: ==17019== Invalid read of size 4 ==17019== at 0x4EFF5B4: virObjectUnref (virobject.c:258) ==17019== by 0x5038CFF: remoteClientCloseFunc (remote_driver.c:552) ==17019== by 0x5069D57: virNetClientCloseLocked (virnetclient.c:685) ==17019== by 0x506C848: virNetClientIncomingEvent (virnetclient.c:1852) ==17019== by 0x5082136: virNetSocketEventHandle (virnetsocket.c:1913) ==17019== by 0x4ECD64E: virEventPollDispatchHandles (vireventpoll.c:509) ==17019== by 0x4ECDE02: virEventPollRunOnce (vireventpoll.c:658) ==17019== by 0x4ECBF00: virEventRunDefaultImpl (virevent.c:308) ==17019== by 0x130386: vshEventLoop (vsh.c:1864) ==17019== by 0x4F1EB07: virThreadHelper (virthread.c:206) ==17019== by 0xA8462D3: start_thread (in /lib64/libpthread-2.20.so) ==17019== by 0xAB441FC: clone (in /lib64/libc-2.20.so) ==17019== Address 0x139023f4 is 4 bytes inside a block of size 240 free'd ==17019== at 0x4C2B1F0: free (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so) ==17019== by 0x4EA8949: virFree (viralloc.c:582) ==17019== by 0x4EFF6D0: virObjectUnref (virobject.c:273) ==17019== by 0x4FE74D6: virConnectClose (libvirt.c:1390) ==17019== by 0x13342A: virshDeinit (virsh.c:406) ==17019== by 0x134A37: main (virsh.c:950) The problem is, when registering remoteClientCloseFunc(), it's conn->closeCallback which is ref'd. But in the function itself it's conn->closeCallback->conn what is unref'd. This is causing imbalance in reference counting. Moreover, there's no need for the remote driver to increase/decrease conn refcount since it's not used anywhere. It's just merely passed to client registered callback. And for that purpose it's correctly ref'd in virConnectRegisterCloseCallback() and then unref'd in virConnectUnregisterCloseCallback(). Signed-off-by: Michal Privoznik (cherry picked from commit e68930077034f786e219bdb015f8880dbc5a246f) Signed-off-by: Michal Privoznik --- src/remote/remote_driver.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/src/remote/remote_driver.c b/src/remote/remote_driver.c index 9a1d78fc4f..b1234ecf89 100644 --- a/src/remote/remote_driver.c +++ b/src/remote/remote_driver.c @@ -518,10 +518,6 @@ remoteClientCloseFunc(virNetClientPtr client ATTRIBUTE_UNUSED, cbdata->freeCallback = NULL; } virObjectUnlock(cbdata); - - /* free the connection reference that comes along with the callback - * registration */ - virObjectUnref(cbdata->conn); } /* helper macro to ease extraction of arguments from the URI */ -- GitLab