[PATCH 6.6 098/166] ocfs2: fix possible deadlock between unlink and dio_end_io_write

Greg Kroah-Hartman
2026-04-24T13:37:39Z

From: Joseph Qi <joseph.qi@linux.alibaba.com>

commit b02da26a992db0c0e2559acbda0fc48d4a2fd337 upstream.

ocfs2_unlink takes orphan dir inode_lock first and then ip_alloc_sem,
while in ocfs2_dio_end_io_write, it acquires these locks in reverse order.
This creates an ABBA lock ordering violation on lock classes
ocfs2_sysfile_lock_key[ORPHAN_DIR_SYSTEM_INODE] and
ocfs2_file_ip_alloc_sem_key.

Lock Chain #0 (orphan dir inode_lock -> ip_alloc_sem):
ocfs2_unlink
ocfs2_prepare_orphan_dir
ocfs2_lookup_lock_orphan_dir
inode_lock(orphan_dir_inode) <- lock A
__ocfs2_prepare_orphan_dir
ocfs2_prepare_dir_for_insert
ocfs2_extend_dir
ocfs2_expand_inline_dir
down_write(&oi->ip_alloc_sem) <- Lock B

Lock Chain #1 (ip_alloc_sem -> orphan dir inode_lock):
ocfs2_dio_end_io_write
down_write(&oi->ip_alloc_sem) <- Lock B
ocfs2_del_inode_from_orphan()
inode_lock(orphan_dir_inode) <- Lock A

Deadlock Scenario:
CPU0 (unlink) CPU1 (dio_end_io_write)
------ ------
inode_lock(orphan_dir_inode)
down_write(ip_alloc_sem)
down_write(ip_alloc_sem)
inode_lock(orphan_dir_inode)

Since ip_alloc_sem is to protect allocation changes, which is unrelated
with operations in ocfs2_del_inode_from_orphan. So move
ocfs2_del_inode_from_orphan out of ip_alloc_sem to fix the deadlock.

Link: https://lkml.kernel.org/r/20260306032211.1016452-1-joseph.qi@linux.alibaba.com
Reported-by: syzbot+67b90111784a3eac8c04@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=67b90111784a3eac8c04
Fixes: a86a72a4a4e0 ("ocfs2: take ip_alloc_sem in ocfs2_dio_get_block & ocfs2_dio_end_io_write")
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ocfs2/aops.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2322,8 +2322,6 @@ static int ocfs2_dio_end_io_write(struct
goto out;
}

- down_write(&oi->ip_alloc_sem);
-
/* Delete orphan before acquire i_rwsem. */
if (dwc->dw_orphaned) {
BUG_ON(dwc->dw_writer_pid != task_pid_nr(current));
@@ -2336,6 +2334,7 @@ static int ocfs2_dio_end_io_write(struct
mlog_errno(ret);
}

+ down_write(&oi->ip_alloc_sem);
di = (struct ocfs2_dinode *)di_bh->b_data;

ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);