[PATCH 6.6 024/121] xfs: introduce protection for drop nlink

6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Cheng Lin <redacted>

commit 2b99e410b28f5a75ae417e6389e767c7745d6fce upstream.

When abnormal drop_nlink are detected on the inode,
return error, to avoid corruption propagation.

Signed-off-by: Cheng Lin <redacted>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
Signed-off-by: Catherine Hoang <redacted>
Acked-by: Chandan Babu R <chandanbabu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/xfs/xfs_inode.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 4d55f58d99b7..fb85c5c81745 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c

@@ -918,6 +918,13 @@ xfs_droplink(
 	xfs_trans_t *tp,
 	xfs_inode_t *ip)
 {
+	if (VFS_I(ip)->i_nlink == 0) {
+		xfs_alert(ip->i_mount,
+			  "%s: Attempt to drop inode (%llu) with nlink zero.",
+			  __func__, ip->i_ino);
+		return -EFSCORRUPTED;
+	}
+
 	xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);
 
 	drop_nlink(VFS_I(ip));

-- 
2.43.0