linux-kernel - [PATCH] fs: Fix bug in lock_rename

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Date:   Mon, 19 Jun 2023 21:37:14 +0800
From:   Li Dong <lidong@...o.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        linux-fsdevel@...r.kernel.org (open list:FILESYSTEMS (VFS and
        infrastructure)), linux-kernel@...r.kernel.org (open list)
Cc:     opensource.kernel@...o.com, lidong@...o.com
Subject: [PATCH] fs: Fix bug in lock_rename_child that can cause deadlock

Function xx causes a deadlock，because s_vfs_rename_mutex was not released when return

Signed-off-by: Li Dong <lidong@...o.com>
---
 fs/namei.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index 91171da719c5..63b3fd05fef2 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3076,8 +3076,10 @@ struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
 	/*
 	 * nobody can move out of any directories on this fs.
 	 */
-	if (likely(c1->d_parent != p2))
+	if (likely(c1->d_parent != p2)) {
+		mutex_unlock(&c1->d_sb->s_vfs_rename_mutex);
 		return lock_two_directories(c1->d_parent, p2);
+	}
 
 	/*
 	 * c1 got moved into p2 while we were taking locks;
-- 
2.31.1.windows.1