Re: [libvirt] [PATCH 3/3] qemu: agent: take monitor lock in qemuAgentNotifyEvent
On 11/24/2016 04:19 AM, Nikolay Shirokovskiy wrote:
qemuAgentNotifyEvent notify on a lock condition without taking
the lock. This works but it is a subject to race conditions.
---
src/qemu/qemu_agent.c | 4 ++++
1 file changed, 4 insertions(+)
But the vm is locked prior to any priv->agent dereference and call - so
what path could free priv->agent before we get into this NotifyEvent
code? I suppose it wouldn't hurt, but we're not entering the agent and
the AgentEOF would require vm lock to clear agent.
John
diff --git a/src/qemu/qemu_agent.c b/src/qemu/qemu_agent.c
index 5230cbc..ad031d0 100644
--- a/src/qemu/qemu_agent.c
+++ b/src/qemu/qemu_agent.c
@@ -1248,6 +1248,8 @@ qemuAgentMakeStringsArray(const char **strings, unsigned int len)
void qemuAgentNotifyEvent(qemuAgentPtr mon,
qemuAgentEvent event)
{
+ virObjectLock(mon);
+
VIR_DEBUG("mon=%p event=%d await_event=%d", mon, event,
mon->await_event);
if (mon->await_event == event) {
mon->await_event = QEMU_AGENT_EVENT_NONE;
@@ -1257,6 +1259,8 @@ void qemuAgentNotifyEvent(qemuAgentPtr mon,
virCondSignal(&mon->notify);
}
}
+
+ virObjectUnlock(mon);
}
VIR_ENUM_DECL(qemuAgentShutdownMode);