[PATCH 1/4] qemu_agent: Rework domain object locking when opening agent

[Michal Privoznik]

Just like qemuMonitorOpen(), hold the domain object locked
throughout the whole time of qemuConnectAgent() and unlock it
only for a brief time of actual connect() (because this is the
only part that has a potential of blocking).

The reason is that qemuAgentOpen() does access domain object
(well, its privateData) AND also at least one argument (@context)
depends on domain object. Accessing these without the lock is
potentially dangerous.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1845468#c12
Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_agent.c   | 3 +++
 src/qemu/qemu_process.c | 4 ----
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_agent.c b/src/qemu/qemu_agent.c
index 5f421be6f6..166cfaf485 100644
--- a/src/qemu/qemu_agent.c
+++ b/src/qemu/qemu_agent.c
@@ -704,7 +704,10 @@ qemuAgentOpen(virDomainObj *vm,
         goto cleanup;
     }
 
+    virObjectUnlock(vm);
     agent->fd = qemuAgentOpenUnix(config->data.nix.path);
+    virObjectLock(vm);
+
     if (agent->fd == -1)
         goto cleanup;
 
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index d5f8a47ac2..d2ea9b55fe 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -238,16 +238,12 @@ qemuConnectAgent(virQEMUDriver *driver, virDomainObj *vm)
      * deleted while the agent is active */
     virObjectRef(vm);
 
-    virObjectUnlock(vm);
-
     agent = qemuAgentOpen(vm,
                           config->source,
                           virEventThreadGetContext(priv->eventThread),
                           &agentCallbacks,
                           virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_VSERPORT_CHANGE));
 
-    virObjectLock(vm);
-
     if (agent == NULL)
         virObjectUnref(vm);
 
-- 
2.32.0