Re: [syzbot] [cgroups?] KASAN: slab-use-after-free Read in pressure_write

[Edward Adam Davis]

#syz test

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 4ca3cb993da2..5a34bd70ef7b 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4280,8 +4280,10 @@ static void cgroup_file_release(struct kernfs_open_file *of)
 	if (cft->release)
 		cft->release(of);
 	put_cgroup_ns(ctx->ns);
+	mutex_lock(&of->mutex);
 	kfree(ctx);
 	of->priv = NULL;
+	mutex_unlock(&of->mutex);
 }
 
 static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,