linux-ext4 - [PATCH] ext4: Fix possible corruption when moving a directory with RENAME

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Date:   Tue, 23 May 2023 15:14:08 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ted Tso <tytso@....edu>
Cc:     <linux-ext4@...r.kernel.org>,
        "Darrick J. Wong" <djwong@...nel.org>, Jan Kara <jack@...e.cz>,
        stable@...r.kernel.org
Subject: [PATCH] ext4: Fix possible corruption when moving a directory with RENAME_EXCHANGE

Commit 0813299c586b ("ext4: Fix possible corruption when moving a
directory") forgot that handling of RENAME_EXCHANGE renames needs the
protection of inode lock when changing directory parents for moved
directories. Add proper locking for that case as well.

CC: stable@...r.kernel.org
Fixes: 0813299c586b ("ext4: Fix possible corruption when moving a directory")
Reported-by: "Darrick J. Wong" <djwong@...nel.org>
Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/ext4/namei.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 45b579805c95..b91abea1c781 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -4083,10 +4083,25 @@ static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
 	if (retval)
 		return retval;
 
+	/*
+	 * We need to protect against old.inode and new.inode directory getting
+	 * converted from inline directory format into a normal one. The lock
+	 * ordering does not matter here as old and new are guaranteed to be
+	 * incomparable in the directory hierarchy.
+	 */
+	if (S_ISDIR(old.inode->i_mode))
+		inode_lock(old.inode);
+	if (S_ISDIR(new.inode->i_mode))
+		inode_lock_nested(new.inode, I_MUTEX_NONDIR2);
+
 	old.bh = ext4_find_entry(old.dir, &old.dentry->d_name,
 				 &old.de, &old.inlined);
-	if (IS_ERR(old.bh))
-		return PTR_ERR(old.bh);
+	if (IS_ERR(old.bh)) {
+		retval = PTR_ERR(old.bh);
+		old.bh = NULL;
+		goto end_rename;
+	}
+
 	/*
 	 *  Check for inode number is _not_ due to possible IO errors.
 	 *  We might rmdir the source, keep it as pwd of some process
@@ -4186,6 +4201,10 @@ static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
 	retval = 0;
 
 end_rename:
+	if (S_ISDIR(old.inode->i_mode))
+		inode_unlock(old.inode);
+	if (S_ISDIR(new.inode->i_mode))
+		inode_unlock(new.inode);
 	brelse(old.dir_bh);
 	brelse(new.dir_bh);
 	brelse(old.bh);
-- 
2.35.3