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

[Viktor Mihajlovski]

On 15.11.2016 13:00, Maxim Nestratov wrote:
> 15-Nov-16 14:26, Viktor Mihajlovski пишет:
> 
>> 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!
>>
> I regard your reply as ACK then.
> Let's wait a bit to let people react to this and if there is no
> objection, I'll push shortly.
> 
> Maxim
> 

I have no ACK-ing credentials, but you can add a

Tested-by: Viktor Mihajlovski <mihajlov at linux.vnet.ibm.com>

Thanks.

-- 

Mit freundlichen Grüßen/Kind Regards
   Viktor Mihajlovski

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