[PATCH v5] xfs: introduce protection for drop nlink

[<cheng.lin130@zte.com.cn>]

From: Cheng Lin <cheng.lin130@zte.com.cn>
When abnormal drop_nlink are detected on the inode,
return error, to avoid corruption propagation.

Signed-off-by: Cheng Lin <cheng.lin130@zte.com.cn>
---
 fs/xfs/xfs_inode.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 9e62cc500..752e6aeba 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -919,6 +919,14 @@ 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));
-- 
2.18.1