[libvirt] [PATCH] qemu: fix libvirtd crash when querying halted cpus info

[Viktor Mihajlovski]

On 02.11.2016 17:29, Viktor Mihajlovski wrote:
> On 02.11.2016 16:56, Maxim Nestratov wrote:
>> It was introduced by commit 7a51d9ebb, which started to use
>> monitor commands without job acquiring, which is unsafe and leads
>> to simultaneous access to vm->mon structure by different threads.
>>
>> Crash backtrace is the following (shortened):
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> qemuMonitorSend (mon=mon at entry=0x7f4ef4000d20, msg=msg at entry=0x7f4f18e78640) at qemu/qemu_monitor.c:1011
>> 1011        while (!mon->msg->finished) {
>>
>> 0  qemuMonitorSend () at qemu/qemu_monitor.c:1011
>> 1  0x00007f691abdc720 in qemuMonitorJSONCommandWithFd () at qemu/qemu_monitor_json.c:298
>> 2  0x00007f691abde64a in qemuMonitorJSONCommand at qemu/qemu_monitor_json.c:328
>> 3  qemuMonitorJSONQueryCPUs at qemu/qemu_monitor_json.c:1408
>> 4  0x00007f691abcaebd in qemuMonitorGetCPUInfo g at entry=false) at qemu/qemu_monitor.c:1931
>> 5  0x00007f691ab96863 in qemuDomainRefreshVcpuHalted at qemu/qemu_domain.c:6309
>> 6  0x00007f691ac0af99 in qemuDomainGetStatsVcpu at qemu/qemu_driver.c:18945
>> 7  0x00007f691abef921 in qemuDomainGetStats  at qemu/qemu_driver.c:19469
>> 8  qemuConnectGetAllDomainStats at qemu/qemu_driver.c:19559
>> 9  0x00007f693382e806 in virConnectGetAllDomainStats at libvirt-domain.c:11546
>> 10 0x00007f6934470c40 in remoteDispatchConnectGetAllDomainStats at remote.c:6267
>>
>> (gdb) p mon->msg
>> $1 = (qemuMonitorMessagePtr) 0x0
>>
>> This change fixes it by calling qemuDomainRefreshVcpuHalted only when job is acquired.
>>
>> Signed-off-by: Maxim Nestratov <mnestratov at virtuozzo.com>
>> ---
>>  src/qemu/qemu_driver.c | 20 +++++++++++++-------
>>  1 file changed, 13 insertions(+), 7 deletions(-)
> [...]
> Argh ... this fell through the cracks when I moved the code from
> vcpuinfo to domstats. Thanks for catching and fixing that one.
> 
It would be nice if the fix could be pushed before the next release
freeze. Thanks!

-- 

Mit freundlichen Grüßen/Kind Regards
   Viktor Mihajlovski

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