linux-kernel - [PATCH] ext4: WARNING: locking bug in ext4

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Message-Id: <20240927165132.17289-1-rbrasga@uci.edu>
Date: Fri, 27 Sep 2024 16:51:32 +0000
From: Remington Brasga <rbrasga@....edu>
To: Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Shuah Khan <skhan@...uxfoundation.org>
Cc: linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-kernel-mentees@...ts.linuxfoundation.org,
	syzbot+a3c8e9ac9f9d77240afd@...kaller.appspotmail.com,
	Remington Brasga <rbrasga@....edu>
Subject: [PATCH] ext4: WARNING: locking bug in ext4_ioctl

Fixed the locking bug with the bisection found by syzbot.

Link to the syzbot bug report:
https://syzkaller.appspot.com/bug?extid=a3c8e9ac9f9d77240afd

Reported-by: syzbot+a3c8e9ac9f9d77240afd@...kaller.appspotmail.com
Signed-off-by: Remington Brasga <rbrasga@....edu>
---
First attempt at patching this issue. Verified the bug exists, and that
this patch fixes it, and EXT4 KUnit tests pass. Though I am not sure if
the patch should be higher up the stack.

Open to questions or any suggestions for improvements.

#syz test

 fs/ext4/xattr.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index e0e1956dcdd3..2b30b9571fd8 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -124,8 +124,12 @@ void ext4_xattr_inode_set_class(struct inode *ea_inode)
 	struct ext4_inode_info *ei = EXT4_I(ea_inode);
 
 	lockdep_set_subclass(&ea_inode->i_rwsem, 1);
-	(void) ei;	/* shut up clang warning if !CONFIG_LOCKDEP */
-	lockdep_set_subclass(&ei->i_data_sem, I_DATA_SEM_EA);
+
+	if (ei->i_flags & EXT4_EA_INODE_FL) {
+		lockdep_set_subclass(&ei->i_data_sem, I_DATA_SEM_EA);
+	} else {
+		lockdep_set_subclass(&ei->i_data_sem, I_DATA_SEM_NORMAL);
+	}
 }
 #endif
 
-- 
2.34.1