[PATCH 6.6.y 1/2] cgroup/psi: Set of->priv to NULL upon file release

[Philo Lu]

From: Chen Ridong <chenridong@xxxxxxxxxx>

commit 94a4acfec14615e971eb2c9e1fa6c992c85ff6c6 upstream.

Setting of->priv to NULL when the file is released enables earlier bug
detection. This allows potential bugs to manifest as NULL pointer
dereferences rather than use-after-free errors[1], which are generally more
difficult to diagnose.

[1] https://lore.kernel.org/cgroups/38ef3ff9-b380-44f0-9315-8b3714b0948d@xxxxxxxxxxxxxxx/T/#m8a3b3f88f0ff3da5925d342e90043394f8b2091b
Signed-off-by: Chen Ridong <chenridong@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Philo Lu <lulie@xxxxxxxxxxxxxxxxx>
---
 kernel/cgroup/cgroup.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index e787dc0eacd7d..4a7d334be50a5 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4061,6 +4061,7 @@ static void cgroup_file_release(struct kernfs_open_file *of)
 		cft->release(of);
 	put_cgroup_ns(ctx->ns);
 	kfree(ctx);
+	of->priv = NULL;
 }
 
 static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
-- 
2.47.3