Patch "xfs: directory scrub should check the null bestfree entries too" has been added to the 5.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    xfs: directory scrub should check the null bestfree entries too

to the 5.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     xfs-directory-scrub-should-check-the-null-bestfree-e.patch
and it can be found in the queue-5.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit cc6afaa477150d6a5dab0c6cc38bfdfa564eba51
Author: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Date:   Sun Nov 8 16:32:42 2020 -0800

    xfs: directory scrub should check the null bestfree entries too
    
    [ 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>

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;