[PATCH 3/6] smb/server: fix invalid pointer dereference in ksmbd_stop_durable_scavenger()

[ZhangGuoDong <zhang.guodong@linux.dev>]

From: ZhangGuoDong <zhangguodong@kylinos.cn>

See the procedure below:

  ksmbd_launch_ksmbd_durable_scavenger
    durable_scavenger_running = true
    server_conf.dh_task = kthread_run() // fail, dh_task is an ERR_PTR()

  server_ctrl_handle_reset
    ksmbd_stop_durable_scavenger
    kthread_stop(server_conf.dh_task) // invalid pointer

Fixes: d484d621d40f ("ksmbd: add durable scavenger timer")
Signed-off-by: ZhangGuoDong <zhangguodong@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/server/vfs_cache.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c
index 5acd06020d42..a35df2ab59c9 100644
--- a/fs/smb/server/vfs_cache.c
+++ b/fs/smb/server/vfs_cache.c
@@ -1618,9 +1618,12 @@ void ksmbd_launch_ksmbd_durable_scavenger(void)
 
 	server_conf.dh_task = kthread_run(ksmbd_durable_scavenger,
 				     (void *)NULL, "ksmbd-durable-scavenger");
-	if (IS_ERR(server_conf.dh_task))
+	if (IS_ERR(server_conf.dh_task)) {
 		pr_err("cannot start conn thread, err : %ld\n",
 		       PTR_ERR(server_conf.dh_task));
+		server_conf.dh_task = NULL;
+		durable_scavenger_running = false;
+	}
 	mutex_unlock(&durable_scavenger_lock);
 }
 
-- 
2.54.0