Commit 08eabe4b authored by Ivan Pravdin's avatar Ivan Pravdin Committed by Andrew Morton
Browse files

ocfs2: avoid potential ABBA deadlock by reordering tl_inode lock 

In ocfs2_move_extent(), tl_inode is currently locked after the global
bitmap inode.  However, in ocfs2_flush_truncate_log(), the lock order is
reversed: tl_inode is locked first, followed by the global bitmap inode.

This creates a classic ABBA deadlock scenario if two threads attempt these
operations concurrently and acquire the locks in different orders.

To prevent this, move the tl_inode locking earlier in ocfs2_move_extent(),
so that it always precedes the global bitmap inode lock.

No functional changes beyond lock ordering.

Link: https://lkml.kernel.org/r/20250708020640.387741-1-ipravdin.official@gmail.com


Reported-by: default avatar <syzbot+6bf948e47f9bac7aacfa@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/all/67d5645c.050a0220.1dc86f.0004.GAE@google.com/


Signed-off-by: default avatarIvan Pravdin <ipravdin.official@gmail.com>
Reviewed-by: default avatarJoseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 97103dce

fs/ocfs2/move_extents.c

+9 −10
Original line number Diff line number Diff line
@@ -617,6 +617,8 @@ static int ocfs2_move_extent(struct ocfs2_move_extents_context *context, 
	 */

	credits += OCFS2_INODE_UPDATE_CREDITS + 1;



	inode_lock(tl_inode);



	/*

	 * ocfs2_move_extent() didn't reserve any clusters in lock_allocators()

	 * logic, while we still need to lock the global_bitmap.
@@ -626,7 +628,7 @@ static int ocfs2_move_extent(struct ocfs2_move_extents_context *context, 
	if (!gb_inode) {

		mlog(ML_ERROR, "unable to get global_bitmap inode\n");

		ret = -EIO;

		goto out;

		goto out_unlock_tl_inode;

	}



	inode_lock(gb_inode);
@@ -634,16 +636,14 @@ static int ocfs2_move_extent(struct ocfs2_move_extents_context *context, 
	ret = ocfs2_inode_lock(gb_inode, &gb_bh, 1);

	if (ret) {

		mlog_errno(ret);

		goto out_unlock_gb_mutex;

		goto out_unlock_gb_inode;

	}



	inode_lock(tl_inode);



	handle = ocfs2_start_trans(osb, credits);

	if (IS_ERR(handle)) {

		ret = PTR_ERR(handle);

		mlog_errno(ret);

		goto out_unlock_tl_inode;

		goto out_unlock;

	}



	new_phys_blkno = ocfs2_clusters_to_blocks(inode->i_sb, *new_phys_cpos);
@@ -703,15 +703,14 @@ static int ocfs2_move_extent(struct ocfs2_move_extents_context *context, 
out_commit:

	ocfs2_commit_trans(osb, handle);

	brelse(gd_bh);



out_unlock_tl_inode:

	inode_unlock(tl_inode);



out_unlock:

	ocfs2_inode_unlock(gb_inode, 1);

out_unlock_gb_mutex:

out_unlock_gb_inode:

	inode_unlock(gb_inode);

	brelse(gb_bh);

	iput(gb_inode);

out_unlock_tl_inode:

	inode_unlock(tl_inode);



out:

	if (context->meta_ac) {