Re: [libvirt] [PATCH 1/2] avoid vm to be deleted if qemuConnectMonitor failed

The reason of libvirtd cores dump is that: We add vm->refs when we alloc the memory, and decrease it in the function qemuHandleMonitorEOF() in other thread. We add vm->refs in the function qemuConnectMonitor() and decrease it when the vm is inactive. The libvirtd will block in the function qemuMonitorSetCapabilities() because the vm is stopped by signal SIGSTOP. Now the vm->refs is 2. Then we kill the vm by signal SIGKILL. The function qemuMonitorSetCapabilities() failed, and then we will decrease vm->refs in the function qemuMonitorClose(). In another thread, mon->fd is broken and the function qemuHandleMonitorEOF() is called. If qemuHandleMonitorEOF() decreases vm->refs before qemuConnectMonitor() returns, vm->refs will be decrease to 0 and the memory is freed. We will call qemudShutdownVMDaemon() as qemuConnectMonitor() failed. The memory has been freed, so qemudShutdownVMDaemon() is too dangerous. We will reference NULL pointer in the function virDomainConfVMNWFilterTeardown(): ============= void virDomainConfVMNWFilterTeardown(virDomainObjPtr vm) { int i; if (nwfilterDriver != NULL) { for (i = 0; i < vm->def->nnets; i++) virDomainConfNWFilterTeardown(vm->def->nets[i]); } } ============ vm->def->nnets is not 0 but vm->def->nets is NULL(We don't set vm->def->nnets to 0 when we free vm). We should add an extra reference of vm to avoid vm to be deleted if qemuConnectMonitor() failed. Signed-off-by: Wen Congyang <wency(a)cn.fujitsu.com&gt;