[04/10] xfs: don't scan off the end of the rt volume in xfs_rtallocate_extent_block

Commit Message

Darrick J. Wong Sept. 2, 2024, 6:28 p.m. UTC

From: Darrick J. Wong <[e-mail]>

The loop conditional here is not quite correct because an rtbitmap block
can represent rtextents beyond the end of the rt volume.  There's no way
that it makes sense to scan for free space beyond EOFS, so don't do it.
This overrun has been present since v2.6.0.

Also fix the type of bestlen, which was incorrectly converted.

Signed-off-by: Darrick J. Wong <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
---
 fs/xfs/xfs_rtalloc.c |   16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

Patch

diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index c65ee8d1d38d..58081ce5247b 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -229,22 +229,20 @@  xfs_rtallocate_extent_block(
 	xfs_rtxnum_t		*rtx)	/* out: start rtext allocated */
 {
 	struct xfs_mount	*mp = args->mp;
-	xfs_rtxnum_t		besti;	/* best rtext found so far */
-	xfs_rtxnum_t		bestlen;/* best length found so far */
+	xfs_rtxnum_t		besti = -1; /* best rtext found so far */
 	xfs_rtxnum_t		end;	/* last rtext in chunk */
-	int			error;
 	xfs_rtxnum_t		i;	/* current rtext trying */
 	xfs_rtxnum_t		next;	/* next rtext to try */
+	xfs_rtxlen_t		bestlen = 0; /* best length found so far */
 	int			stat;	/* status from internal calls */
+	int			error;
 
 	/*
-	 * Loop over all the extents starting in this bitmap block,
-	 * looking for one that's long enough.
+	 * Loop over all the extents starting in this bitmap block up to the
+	 * end of the rt volume, looking for one that's long enough.
 	 */
-	for (i = xfs_rbmblock_to_rtx(mp, bbno), besti = -1, bestlen = 0,
-		end = xfs_rbmblock_to_rtx(mp, bbno + 1) - 1;
-	     i <= end;
-	     i++) {
+	end = min(mp->m_sb.sb_rextents, xfs_rbmblock_to_rtx(mp, bbno + 1)) - 1;
+	for (i = xfs_rbmblock_to_rtx(mp, bbno); i <= end; i++) {
 		/* Make sure we don't scan off the end of the rt volume. */
 		maxlen = xfs_rtallocate_clamp_len(mp, i, maxlen, prod);