Patch "net: gso: fix tcp fraglist segmentation after pull from frag_list" has been added to the 6.6-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    net: gso: fix tcp fraglist segmentation after pull from frag_list

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-gso-fix-tcp-fraglist-segmentation-after-pull-from-frag_list.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-222524-greg=kroah.com@vger.kernel.org Mon Mar  2 07:56:08 2026
From: Li hongliang <1468888505@139.com>
Date: Mon,  2 Mar 2026 14:55:22 +0800
Subject: net: gso: fix tcp fraglist segmentation after pull from frag_list
To: gregkh@linuxfoundation.org, stable@vger.kernel.org, nbd@nbd.name
Cc: patches@lists.linux.dev, linux-kernel@vger.kernel.org, edumazet@google.com, davem@davemloft.net, dsahern@kernel.org, kuba@kernel.org, pabeni@redhat.com, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, willemb@google.com, netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, bpf@vger.kernel.org
Message-ID: <20260302065522.2695626-1-1468888505@139.com>

From: Felix Fietkau <nbd@nbd.name>

[ Upstream commit 17bd3bd82f9f79f3feba15476c2b2c95a9b11ff8 ]

Detect tcp gso fraglist skbs with corrupted geometry (see below) and
pass these to skb_segment instead of skb_segment_list, as the first
can segment them correctly.

Valid SKB_GSO_FRAGLIST skbs
- consist of two or more segments
- the head_skb holds the protocol headers plus first gso_size
- one or more frag_list skbs hold exactly one segment
- all but the last must be gso_size

Optional datapath hooks such as NAT and BPF (bpf_skb_pull_data) can
modify these skbs, breaking these invariants.

In extreme cases they pull all data into skb linear. For TCP, this
causes a NULL ptr deref in __tcpv4_gso_segment_list_csum at
tcp_hdr(seg->next).

Detect invalid geometry due to pull, by checking head_skb size.
Don't just drop, as this may blackhole a destination. Convert to be
able to pass to regular skb_segment.

Approach and description based on a patch by Willem de Bruijn.

Link: https://lore.kernel.org/netdev/20240428142913.18666-1-shiming.cheng@mediatek.com/
Link: https://lore.kernel.org/netdev/20240922150450.3873767-1-willemdebruijn.kernel@gmail.com/
Fixes: bee88cd5bd83 ("net: add support for segmenting TCP fraglist GSO packets")
Cc: stable@vger.kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20240926085315.51524-1-nbd@nbd.name
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Li hongliang <1468888505@139.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp_offload.c   |   10 ++++++++--
 net/ipv6/tcpv6_offload.c |   10 ++++++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -104,8 +104,14 @@ static struct sk_buff *tcp4_gso_segment(
 	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
 		return ERR_PTR(-EINVAL);
 
-	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST)
-		return __tcp4_gso_segment_list(skb, features);
+	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
+		struct tcphdr *th = tcp_hdr(skb);
+
+		if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size)
+			return __tcp4_gso_segment_list(skb, features);
+
+		skb->ip_summed = CHECKSUM_NONE;
+	}
 
 	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
 		const struct iphdr *iph = ip_hdr(skb);
--- a/net/ipv6/tcpv6_offload.c
+++ b/net/ipv6/tcpv6_offload.c
@@ -106,8 +106,14 @@ static struct sk_buff *tcp6_gso_segment(
 	if (!pskb_may_pull(skb, sizeof(*th)))
 		return ERR_PTR(-EINVAL);
 
-	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST)
-		return __tcp6_gso_segment_list(skb, features);
+	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
+		struct tcphdr *th = tcp_hdr(skb);
+
+		if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size)
+			return __tcp6_gso_segment_list(skb, features);
+
+		skb->ip_summed = CHECKSUM_NONE;
+	}
 
 	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
 		const struct ipv6hdr *ipv6h = ipv6_hdr(skb);


Patches currently in stable-queue which might be from 1468888505@139.com are

queue-6.6/pnfs-fix-a-deadlock-when-returning-a-delegation-during-open.patch
queue-6.6/net-add-support-for-segmenting-tcp-fraglist-gso-packets.patch
queue-6.6/net-fix-segmentation-of-forwarding-fraglist-gro.patch
queue-6.6/nfs-pass-explicit-offset-count-to-trace-events.patch
queue-6.6/net-gso-fix-tcp-fraglist-segmentation-after-pull-from-frag_list.patch
queue-6.6/nfs-fix-a-deadlock-involving-nfs_release_folio.patch