FAILED: patch "[PATCH] net: thunderbolt: Fix frags[] overflow by bounding" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 55d9895f89970501fe126d1026b586b04a224c27
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026072026-jab-puzzling-567e@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 55d9895f89970501fe126d1026b586b04a224c27 Mon Sep 17 00:00:00 2001
From: Maoyi Xie <maoyixie.tju@gmail.com>
Date: Wed, 17 Jun 2026 01:38:41 +0800
Subject: [PATCH] net: thunderbolt: Fix frags[] overflow by bounding
 frame_count

tbnet_poll() assembles a multi-frame ThunderboltIP packet into one skb. The
first frame goes into the skb linear area and every further frame is added as
a page fragment.

	skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
			page, hdr_size, frame_size,
			TBNET_RX_PAGE_SIZE - hdr_size);

A packet of frame_count frames therefore ends up with frame_count - 1
fragments. tbnet_check_frame() only bounds the peer supplied frame_count to
TBNET_RING_SIZE / 4 (64), which is far above MAX_SKB_FRAGS (17 by default). A
peer that sends a packet of 19 or more small frames pushes nr_frags past
MAX_SKB_FRAGS, so skb_add_rx_frag() writes past skb_shinfo()->frags[] and
corrupts memory after the shared info.

Tighten the start of packet bound to MAX_SKB_FRAGS + 1 so a packet can never
produce more fragments than frags[] can hold. This matches the recent skb
frags overflow fixes in other receive paths, for example f0813bcd2d9d ("net:
wwan: t7xx: fix potential skb->frags overflow in RX path") and 600dc40554dc
("net: usb: cdc-phonet: fix skb frags[] overflow in rx_complete()").

Fixes: e69b6c02b4c3 ("net: Add support for networking over Thunderbolt cable")
Cc: stable@vger.kernel.org
Signed-off-by: Maoyi Xie <maoyixie.tju@gmail.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://patch.msgid.link/178163152194.2486768.14724194232649760778@maoyixie.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
index 7aae5d915a1e..ac016890646c 100644
--- a/drivers/net/thunderbolt/main.c
+++ b/drivers/net/thunderbolt/main.c
@@ -787,8 +787,12 @@ static bool tbnet_check_frame(struct tbnet *net, const struct tbnet_frame *tf,
 		return true;
 	}
 
-	/* Start of packet, validate the frame header */
-	if (frame_count == 0 || frame_count > TBNET_RING_SIZE / 4) {
+	/* Start of packet, validate the frame header. tbnet_poll() puts the
+	 * first frame in the skb linear area and every further frame in a page
+	 * fragment, so a packet may not span more than MAX_SKB_FRAGS + 1 frames
+	 * without overflowing skb_shinfo()->frags[].
+	 */
+	if (frame_count == 0 || frame_count > MAX_SKB_FRAGS + 1) {
 		net->stats.rx_length_errors++;
 		return false;
 	}