FAILED: patch "[PATCH] NFSv4/pnfs: bound the CB_NOTIFY_DEVICEID array count before" 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 32f0967ea296d447925465c98e7eec71d4e2f755
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026110400-plexiglas-ladder-a8f1@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 32f0967ea296d447925465c98e7eec71d4e2f755 Mon Sep 17 00:00:00 2001
From: Benjamin Coddington <ben.coddington@hammerspace.com>
Date: Tue, 15 Sep 2026 08:22:05 -0400
Subject: [PATCH] NFSv4/pnfs: bound the CB_NOTIFY_DEVICEID array count before
 allocating

decode_devicenotify_args() hands the server's notification count
straight to kmalloc_objs() as the array length, without checking it
against the message that carried it.  Bound it the way nfs4xdr.c bounds
an attribute length, against xdr_stream_remaining().

Fixes: 1be5683b03a7 ("pnfs: CB_NOTIFY_DEVICEID")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-fable-5
Signed-off-by: Benjamin Coddington <bcodding@hammerspace.com>
Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com>

diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
index 88e1af0fda01..b1bc2c02b5a6 100644
--- a/fs/nfs/callback_xdr.c
+++ b/fs/nfs/callback_xdr.c
@@ -271,6 +271,13 @@ __be32 decode_devicenotify_args(struct svc_rqst *rqstp,
 	if (n == 0)
 		goto out;
 
+	/* sanity check the count against the remaining stream */
+	if (n > xdr_stream_remaining(xdr) /
+		((4 * sizeof(uint32_t)) + NFS4_DEVICEID4_SIZE)) {
+		status = htonl(NFS4ERR_BADXDR);
+		goto out;
+	}
+
 	args->devs = kmalloc_objs(*args->devs, n);
 	if (!args->devs) {
 		status = htonl(NFS4ERR_DELAY);