xfs: introduce protection for drop nlink

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>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 4d55f58d99b7ac0333b725fa7baf6f1f62b7fc98..fb85c5c8174523c60d11884e989f7d2331e6e14b 100644 (file)
--- 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));