On 9/28/22 15:53, Jiang Jiacheng wrote:
> In the case of concurrent VM operations, it is possible to have a null pointer
> reference in qemuMonitorOpen. In the case of concurrent VM shutdown, the
> priv->monconf will be changed in qemuProcessStop. qemuMonitorOpen releases the
> lock before calling qemuMonitorOpenUnix and then references priv->monconf. The
> path variable in monconf will cause a null pointer, so it's better to back up the
> path content in monconf before releasing the lock.
>
> Signed-off-by: Jiang Jiacheng <jiangjiacheng@xxxxxxxxxx>
> ---
> src/qemu/qemu_monitor.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
> index c2808c75a3..792b895570 100644
> --- a/src/qemu/qemu_monitor.c
> +++ b/src/qemu/qemu_monitor.c
> @@ -679,6 +679,7 @@ qemuMonitorOpen(virDomainObj *vm,
> {
> VIR_AUTOCLOSE fd = -1;
> qemuMonitor *ret = NULL;
> + g_aurofree char *path = NULL;
>
> if (config->type != VIR_DOMAIN_CHR_TYPE_UNIX) {
> virReportError(VIR_ERR_INTERNAL_ERROR,
> @@ -687,8 +688,10 @@ qemuMonitorOpen(virDomainObj *vm,
> return NULL;
> }
>
> + path = g_strdup(config->data.nix.path);
> +
> virObjectUnlock(vm);
> - fd = qemuMonitorOpenUnix(config->data.nix.path);
> + fd = qemuMonitorOpenUnix(path);
> virObjectLock(vm);
>
> if (fd < 0)
I'm failing to see how is this possible. Connecting to a monitor
inherently has a job, qemuProcessStop also has a job, inherently.
And even if there was a path, the @config is an object and all that
qemuProcessStop does is just unrefs it. Hence, a path string being freed
seems more like a refcounting issue to me. Thus, this looks more correct:
diff --git c/src/qemu/qemu_monitor.c w/src/qemu/qemu_monitor.c
index 5eba154d96..286f0ae7ff 100644
--- c/src/qemu/qemu_monitor.c
+++ w/src/qemu/qemu_monitor.c
@@ -687,9 +687,11 @@ qemuMonitorOpen(virDomainObj *vm,
return NULL;
}
+ virObjectRef(config);
virObjectUnlock(vm);
fd = qemuMonitorOpenUnix(config->data.nix.path);
virObjectLock(vm);
+ virObjectUnref(config);
if (fd < 0)
return NULL;
Michal
