FAILED: patch "[PATCH] ceph: fix 32-bit overflow in readdir reply count check" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.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 52913831ba56efceaafd80b501d68fa00f79bde6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107061210-failed-5.15-52913831ba56@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

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

From 52913831ba56efceaafd80b501d68fa00f79bde6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= <Jeremy.Jean@oss.cyber.gouv.fr>
Date: Wed, 23 Sep 2026 20:25:34 +0000
Subject: [PATCH] ceph: fix 32-bit overflow in readdir reply count check
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

parse_reply_info_readdir() checks how many entries are in a readdir
reply by computing the end pointer of the decoded array. That pointer
addition can wrap on 32-bit kernels and let an oversized count pass the
check. For example, a count of 0x40000000 with 156-byte entries wraps
to a zero offset, so the decoder can write past the preallocated buffer.

Check the count against the number of entries that fit in the allocation
before publishing dir_nr. Reject oversized replies through the existing
error path.

Cc: stable@vger.kernel.org
Fixes: 54008399dc0c ("ceph: preallocate buffer for readdir reply")
Assisted-by: LLM
Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---
 fs/ceph/mds_client.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index a207b342e7dae..9f13f3f7b800f 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -504,10 +504,8 @@ static int parse_reply_info_readdir(void **p, void *end,
 		goto done;
 
 	BUG_ON(!info->dir_entries);
-	if ((unsigned long)(info->dir_entries + num) >
-	    (unsigned long)info->dir_entries + info->dir_buf_size) {
+	if (num > info->dir_buf_size / sizeof(*info->dir_entries)) {
 		pr_err_client(cl, "dir contents are larger than expected\n");
-		WARN_ON(1);
 		goto bad;
 	}
 
-- 
2.53.0