[PATCH 5.9 162/252] xfs: directory scrub should check the null bestfree entries too

[Greg Kroah-Hartman]

From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>

[ Upstream commit 6b48e5b8a20f653b7d64ccf99a498f2523bff752 ]

Teach the directory scrubber to check all the bestfree entries,
including the null ones.  We want to be able to detect the case where
the entry is null but there actually /is/ a directory data block.

Found by fuzzing lbests[0] = ones in xfs/391.

Fixes: df481968f33b ("xfs: scrub directory freespace")
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/xfs/scrub/dir.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/scrub/dir.c b/fs/xfs/scrub/dir.c
index 7c432997edade..b045e95c2ea73 100644
--- a/fs/xfs/scrub/dir.c
+++ b/fs/xfs/scrub/dir.c
@@ -558,14 +558,27 @@ xchk_directory_leaf1_bestfree(
 	/* Check all the bestfree entries. */
 	for (i = 0; i < bestcount; i++, bestp++) {
 		best = be16_to_cpu(*bestp);
-		if (best == NULLDATAOFF)
-			continue;
 		error = xfs_dir3_data_read(sc->tp, sc->ip,
-				i * args->geo->fsbcount, 0, &dbp);
+				xfs_dir2_db_to_da(args->geo, i),
+				XFS_DABUF_MAP_HOLE_OK,
+				&dbp);
 		if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, lblk,
 				&error))
 			break;
-		xchk_directory_check_freesp(sc, lblk, dbp, best);
+
+		if (!dbp) {
+			if (best != NULLDATAOFF) {
+				xchk_fblock_set_corrupt(sc, XFS_DATA_FORK,
+						lblk);
+				break;
+			}
+			continue;
+		}
+
+		if (best == NULLDATAOFF)
+			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
+		else
+			xchk_directory_check_freesp(sc, lblk, dbp, best);
 		xfs_trans_brelse(sc->tp, dbp);
 		if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
 			break;
-- 
2.27.0