Re: [libvirt] [PATCH 2/2] qemu: Avoid operations on NULL monitor if VM fails early

On 14.01.2014 19:31, Peter Krempa wrote: > https://bugzilla.redhat.com/show_bug.cgi?id=1047659 > > If a VM dies very early during an attempted connect to the guest agent > while the locks are down the domain monitor object will be freed. The > object is then accessed later as any failure during guest agent startup > isn't considered fatal. > > In the current upstream version this doesn't lead to a crash as > virObjectLock called when entering the monitor in > qemuProcessDetectVcpuPIDs checks the pointer before attempting to > dereference (lock) it. The NULL pointer is then caught in the monitor > helper code. > > Before the introduction of virObjectLockable - observed on 0.10.2 - the > pointer is locked directly via virMutexLock leading to a crash. > > To avoid this problem we need to differentiate between the guest agent > not being present and the VM quitting when the locks were down. The fix > reorganizes the code in qemuConnectAgent to add the check and then adds > special handling to the callers. > --- > src/qemu/qemu_process.c | 34 +++++++++++++++++++++++++--------- > 1 file changed, 25 insertions(+), 9 deletions(-) > ACK and safe for 1.2.1. Michal