xfs: don't accept inode buffers with suspicious unlinked chains

When we're verifying inode buffers, sanity-check the unlinked pointer.
We don't want to run the risk of trying to purge something that's
obviously broken.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/libxfs/xfs_inode_buf.c

@@ -93,20 +93,26 @@ xfs_inode_buf_verify(
 	bool		readahead)
 {
 	struct xfs_mount *mp = bp->b_target->bt_mount;
+	xfs_agnumber_t	agno;
 	int		i;
 	int		ni;
 
 	/*
 	 * Validate the magic number and version of every inode in the buffer
 	 */
+	agno = xfs_daddr_to_agno(mp, XFS_BUF_ADDR(bp));
 	ni = XFS_BB_TO_FSB(mp, bp->b_length) * mp->m_sb.sb_inopblock;
 	for (i = 0; i < ni; i++) {
 		int		di_ok;
 		xfs_dinode_t	*dip;
+		xfs_agino_t	unlinked_ino;
 
 		dip = xfs_buf_offset(bp, (i << mp->m_sb.sb_inodelog));
+		unlinked_ino = be32_to_cpu(dip->di_next_unlinked);
 		di_ok = dip->di_magic == cpu_to_be16(XFS_DINODE_MAGIC) &&
-			xfs_dinode_good_version(mp, dip->di_version);
+			xfs_dinode_good_version(mp, dip->di_version) &&
+			(unlinked_ino == NULLAGINO ||
+			 xfs_verify_agino(mp, agno, unlinked_ino));
 		if (unlikely(XFS_TEST_ERROR(!di_ok, mp,
 						XFS_ERRTAG_ITOBP_INOTOBP))) {
 			if (readahead) {
@@ -124,9 +130,9 @@ xfs_inode_buf_verify(
 			xfs_buf_verifier_error(bp, -EFSCORRUPTED,
 					__func__, dip, sizeof(*dip),
 					NULL);
+			return;
 		}
 	}
-	xfs_inobp_check(mp, bp);
 }