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Subject: FAILED: patch "[PATCH] xfs: strengthen the "is cow staging" helpers in scrub" failed to apply to 5.15-stable tree
To: djwong@kernel.org,cem@kernel.org,hch@lst.de
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Wed, 16 Sep 2026 18:21:09 +0100
Message-ID: <2026091609-voting-wager-2b45@gregkh>
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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 0d43368844a75ad13561a1198a3b027940730756
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026091609-voting-wager-2b45@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 0d43368844a75ad13561a1198a3b027940730756 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@kernel.org>
Date: Wed, 2 Sep 2026 22:51:36 -0700
Subject: [PATCH] xfs: strengthen the "is cow staging" helpers in scrub

LOLLM pointed out a bug in both of the refcount scrub predicates that
determine if a range of blocks is marked as CoW staging in the btree.
While it compares blockcount < len, this isn't enough to determine that
the CoW staging record is at least as large as the range passed into the
helper.  Fix both of them.

Cc: stable@vger.kernel.org # v4.16
Fixes: f6d5fc21fdc713 ("xfs: cross-reference refcount btree during scrub")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Assisted-by: LOLLM # finding obvious bugs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/fs/xfs/scrub/refcount.c b/fs/xfs/scrub/refcount.c
index f2addaf13c58..f8c51d8fbb3d 100644
--- a/fs/xfs/scrub/refcount.c
+++ b/fs/xfs/scrub/refcount.c
@@ -581,8 +581,12 @@ xchk_xref_is_cow_staging(
 	if (rc.rc_domain != XFS_REFC_DOMAIN_COW)
 		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
 
+	/* Can't start after bno */
+	if (rc.rc_startblock > agbno)
+		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
+
 	/* Must be at least as long as what was passed in */
-	if (rc.rc_blockcount < len)
+	if (rc.rc_startblock + rc.rc_blockcount < agbno + len)
 		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
 }
 
diff --git a/fs/xfs/scrub/rtrefcount.c b/fs/xfs/scrub/rtrefcount.c
index a024d50cf9d2..652d6b78b7a0 100644
--- a/fs/xfs/scrub/rtrefcount.c
+++ b/fs/xfs/scrub/rtrefcount.c
@@ -609,8 +609,12 @@ xchk_xref_is_rt_cow_staging(
 	if (rc.rc_domain != XFS_REFC_DOMAIN_COW)
 		xchk_btree_xref_set_corrupt(sc, sc->sr.refc_cur, 0);
 
+	/* Can't start after bno */
+	if (rc.rc_startblock > bno)
+		xchk_btree_xref_set_corrupt(sc, sc->sr.refc_cur, 0);
+
 	/* Must be at least as long as what was passed in */
-	if (rc.rc_blockcount < len)
+	if (rc.rc_startblock + rc.rc_blockcount < bno + len)
 		xchk_btree_xref_set_corrupt(sc, sc->sr.refc_cur, 0);
 }