FAILED: patch "[PATCH] xfs: fix zero byte checking in the superblock scrubber" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x c004a793e0ec34047c3bd423bcd8966f5fac88dc
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024121522-parcel-pebble-9775@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c004a793e0ec34047c3bd423bcd8966f5fac88dc Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@kernel.org>
Date: Mon, 2 Dec 2024 10:57:42 -0800
Subject: [PATCH] xfs: fix zero byte checking in the superblock scrubber

The logic to check that the region past the end of the superblock is all
zeroes is wrong -- we don't want to check only the bytes past the end of
the maximally sized ondisk superblock structure as currently defined in
xfs_format.h; we want to check the bytes beyond the end of the ondisk as
defined by the feature bits.

Port the superblock size logic from xfs_repair and then put it to use in
xfs_scrub.

Cc: <stable@vger.kernel.org> # v4.15
Fixes: 21fb4cb1981ef7 ("xfs: scrub the secondary superblocks")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/scrub/agheader.c b/fs/xfs/scrub/agheader.c
index 88063d67cb5f..9f8c312dfd3c 100644
--- a/fs/xfs/scrub/agheader.c
+++ b/fs/xfs/scrub/agheader.c
@@ -59,6 +59,32 @@ xchk_superblock_xref(
 	/* scrub teardown will take care of sc->sa for us */
 }
 
+/*
+ * Calculate the ondisk superblock size in bytes given the feature set of the
+ * mounted filesystem (aka the primary sb).  This is subtlely different from
+ * the logic in xfs_repair, which computes the size of a secondary sb given the
+ * featureset listed in the secondary sb.
+ */
+STATIC size_t
+xchk_superblock_ondisk_size(
+	struct xfs_mount	*mp)
+{
+	if (xfs_has_metadir(mp))
+		return offsetofend(struct xfs_dsb, sb_pad);
+	if (xfs_has_metauuid(mp))
+		return offsetofend(struct xfs_dsb, sb_meta_uuid);
+	if (xfs_has_crc(mp))
+		return offsetofend(struct xfs_dsb, sb_lsn);
+	if (xfs_sb_version_hasmorebits(&mp->m_sb))
+		return offsetofend(struct xfs_dsb, sb_bad_features2);
+	if (xfs_has_logv2(mp))
+		return offsetofend(struct xfs_dsb, sb_logsunit);
+	if (xfs_has_sector(mp))
+		return offsetofend(struct xfs_dsb, sb_logsectsize);
+	/* only support dirv2 or more recent */
+	return offsetofend(struct xfs_dsb, sb_dirblklog);
+}
+
 /*
  * Scrub the filesystem superblock.
  *
@@ -75,6 +101,7 @@ xchk_superblock(
 	struct xfs_buf		*bp;
 	struct xfs_dsb		*sb;
 	struct xfs_perag	*pag;
+	size_t			sblen;
 	xfs_agnumber_t		agno;
 	uint32_t		v2_ok;
 	__be32			features_mask;
@@ -388,8 +415,8 @@ xchk_superblock(
 	}
 
 	/* Everything else must be zero. */
-	if (memchr_inv(sb + 1, 0,
-			BBTOB(bp->b_length) - sizeof(struct xfs_dsb)))
+	sblen = xchk_superblock_ondisk_size(mp);
+	if (memchr_inv((char *)sb + sblen, 0, BBTOB(bp->b_length) - sblen))
 		xchk_block_set_corrupt(sc, bp);
 
 	xchk_superblock_xref(sc, bp);