Forwarded: [PATCH] jfs: fix KMSAN warning in txLock

syzbot
2026-01-23T05:12:35Z

Subject: [PATCH] jfs: fix KMSAN warning in txLock
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Syzbot reported a KMSAN uninit-value warning in txLock when accessing
jfs_ip->atlhead:

BUG: KMSAN: uninit-value in txLock+0x13a2/0x2900 fs/jfs/jfs_txnmgr.c:659

This occurs because the jfs_inode_info structure is allocated from a
slab cache but not fully initialized, leaving fields like atlhead,
atltail, and anon_inode_list with garbage values from previously freed
inodes.

When txLock() attempts to traverse the anonymous transaction lock list
by reading jfs_ip->atlhead, it accesses uninitialized memory, triggering
the KMSAN warning.

Fix this by zeroing the entire jfs_inode_info structure in
jfs_alloc_inode(). This is consistent with how other filesystems handle
inode allocation and ensures all fields start with known values,
preventing this and potential similar bugs.

Reported-by: syzbot+d3a57c32b9112d7b01ec@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d3a57c32b9112d7b01ec
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
fs/jfs/super.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index 3cfb86c5a36e..236fe8d42542 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -105,9 +105,7 @@ static struct inode *jfs_alloc_inode(struct super_block *sb)
jfs_inode = alloc_inode_sb(sb, jfs_inode_cachep, GFP_NOFS);
if (!jfs_inode)
return NULL;
-#ifdef CONFIG_QUOTA
- memset(&jfs_inode->i_dquot, 0, sizeof(jfs_inode->i_dquot));
-#endif
+ memset(jfs_inode, 0, sizeof(struct jfs_inode_info));
return &jfs_inode->vfs_inode;
}

--
2.43.0