From 2454ad83b90afbc6ed2c22ec1310b624c40bf0d3 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 1 Jun 2023 12:58:26 +0200
Subject: [PATCH] fs: Restrict lock_two_nondirectories() to non-directory
 inodes
Git-commit: 2454ad83b90afbc6ed2c22ec1310b624c40bf0d3
Patch-mainline: v6.5-rc1
References: bsc#1221044 CVE-2023-52591

Currently lock_two_nondirectories() is skipping any passed directories.
After vfs_rename() uses lock_two_inodes(), all the remaining four users
of this function pass only regular files to it. So drop the somewhat
unusual "skip directory" logic and instead warn if anybody passes
directory to it. This also allows us to use lock_two_inodes() in
lock_two_nondirectories() to concentrate the lock ordering logic in less
places.

Signed-off-by: Jan Kara <jack@suse.cz>
Message-id: <20230601105830.13168-6-jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/inode.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index b9d498032270..53ae3b76d232 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1148,7 +1148,7 @@ void lock_two_inodes(struct inode *inode1, struct inode *inode2,
 /**
  * lock_two_nondirectories - take two i_mutexes on non-directory objects
  *
- * Lock any non-NULL argument that is not a directory.
+ * Lock any non-NULL argument. Passed objects must not be directories.
  * Zero, one or two objects may be locked by this function.
  *
  * @inode1: first inode to lock
@@ -1156,13 +1156,9 @@ void lock_two_inodes(struct inode *inode1, struct inode *inode2,
  */
 void lock_two_nondirectories(struct inode *inode1, struct inode *inode2)
 {
-	if (inode1 > inode2)
-		swap(inode1, inode2);
-
-	if (inode1 && !S_ISDIR(inode1->i_mode))
-		inode_lock(inode1);
-	if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
-		inode_lock_nested(inode2, I_MUTEX_NONDIR2);
+	WARN_ON_ONCE(S_ISDIR(inode1->i_mode));
+	WARN_ON_ONCE(S_ISDIR(inode2->i_mode));
+	lock_two_inodes(inode1, inode2, I_MUTEX_NORMAL, I_MUTEX_NONDIR2);
 }
 EXPORT_SYMBOL(lock_two_nondirectories);
 
@@ -1173,10 +1169,14 @@ EXPORT_SYMBOL(lock_two_nondirectories);
  */
 void unlock_two_nondirectories(struct inode *inode1, struct inode *inode2)
 {
-	if (inode1 && !S_ISDIR(inode1->i_mode))
+	if (inode1) {
+		WARN_ON_ONCE(S_ISDIR(inode1->i_mode));
 		inode_unlock(inode1);
-	if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
+	}
+	if (inode2 && inode2 != inode1) {
+		WARN_ON_ONCE(S_ISDIR(inode2->i_mode));
 		inode_unlock(inode2);
+	}
 }
 EXPORT_SYMBOL(unlock_two_nondirectories);
 
-- 
2.35.3