Commit 66817a979426 for kernel
commit 66817a9794263cd2a5dc4e99bf8e5fcc5ff7181e
Author: HW He <hw.he@mediatek.com>
Date: Tue Sep 1 16:23:12 2026 +0800
net: gro: Fix nesting of TCP GSO SKBs in skb_gro_receive_list()
Fraglist GRO and hardware GRO can create an fraglist of
HW-GRO packets. This cannot be segmented back into
the original form on TCP tethering scenario.
Avoid constructing such a GSO packet, by flushing an already
built fraglist GRO packet if a hardware GRO packet arrives.
Scenario (Tethering/Forwarding):
1.Driver submits a single TCP packet, P1. P1 is kept in the
gro_list as the first packet.
2. The driver submits a TCP GSO skb, P2. P2 has already aggregated
multiple TCP packets by HW_GRO, and its non-linear data is stored in
frags[].
3. P1 and P2 match the GRO rules, and since there is no local socket,
they are aggregated by skb_gro_receive_list(). The resulting skb,
P3, has a frag_list entry that still contains frags[]:
P3: [ Linear Data ] -> frag_list -> [ Linear Data ]
[ frag[1] ]
[ frag[2] ]
...
4. Later, tcp4_gso_segment() or tcp6_gso_segment() calls
skb_segment_list() to segment P3. However, skb_segment_list() only
segments the entries in frag_list. It does not segment the frags[]
inside P2, so P3 is not restored to the original packets, which leads
to IP fragmentation or packet drop in the following path.
Check skb_is_gso(skb) and current GRO method, make sure fraglist GRO
applies to consecutive non-GSO skb, others adopt regular GRO path.
Fixes: 8d95dc474f85 ("net: add code for TCP fraglist GRO")
Signed-off-by: Zhaoping Shu <zhaoping.shu@mediatek.com>
Signed-off-by: HW He <hw.he@mediatek.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260901082312.14596-1-zhaoping.shu@mediatek.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 3b1fdcd3cb29..e74d99ca9fac 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -332,6 +332,7 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb,
flush |= skb->ip_summed != p->ip_summed;
flush |= skb->csum_level != p->csum_level;
flush |= NAPI_GRO_CB(p)->count >= 64;
+ flush |= NAPI_GRO_CB(p)->is_flist != NAPI_GRO_CB(skb)->is_flist;
skb_set_network_header(skb, skb_gro_receive_network_offset(skb));
if (flush || skb_gro_receive_list(p, skb))
@@ -395,12 +396,20 @@ static void tcp4_check_fraglist_gro(struct list_head *head, struct sk_buff *skb,
struct net *net;
int iif, sdif;
- if (likely(!(skb->dev->features & NETIF_F_GRO_FRAGLIST)))
- return;
-
p = tcp_gro_lookup(head, th);
if (p) {
- NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist;
+ /* flist GRO applies to consecutive non-GSO skbs */
+ if (!skb_is_gso(skb) || !NAPI_GRO_CB(p)->is_flist) {
+ NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist;
+ return;
+ }
+
+ /* Fall back to the regular GRO path */
+ if (NAPI_GRO_CB(p)->count == 1)
+ NAPI_GRO_CB(p)->is_flist = 0;
+
+ NAPI_GRO_CB(skb)->is_flist = 0;
+
return;
}
@@ -410,7 +419,7 @@ static void tcp4_check_fraglist_gro(struct list_head *head, struct sk_buff *skb,
sk = __inet_lookup_established(net, iph->saddr, th->source,
iph->daddr, ntohs(th->dest),
iif, sdif);
- NAPI_GRO_CB(skb)->is_flist = !sk;
+ NAPI_GRO_CB(skb)->is_flist = !sk && !skb_is_gso(skb);
if (sk)
sock_gen_put(sk);
}
@@ -430,7 +439,8 @@ struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
if (!th)
goto flush;
- tcp4_check_fraglist_gro(head, skb, th);
+ if (unlikely(skb->dev->features & NETIF_F_GRO_FRAGLIST))
+ tcp4_check_fraglist_gro(head, skb, th);
return tcp_gro_receive(head, skb, th);
diff --git a/net/ipv6/tcpv6_offload.c b/net/ipv6/tcpv6_offload.c
index f2a659cd6183..eec3778855eb 100644
--- a/net/ipv6/tcpv6_offload.c
+++ b/net/ipv6/tcpv6_offload.c
@@ -26,7 +26,18 @@ static void tcp6_check_fraglist_gro(struct list_head *head, struct sk_buff *skb,
p = tcp_gro_lookup(head, th);
if (p) {
- NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist;
+ /* flist GRO applies to consecutive non-GSO skbs */
+ if (!skb_is_gso(skb) || !NAPI_GRO_CB(p)->is_flist) {
+ NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist;
+ return;
+ }
+
+ /* Fall back to the regular GRO path */
+ if (NAPI_GRO_CB(p)->count == 1)
+ NAPI_GRO_CB(p)->is_flist = 0;
+
+ NAPI_GRO_CB(skb)->is_flist = 0;
+
return;
}
@@ -36,7 +47,7 @@ static void tcp6_check_fraglist_gro(struct list_head *head, struct sk_buff *skb,
sk = __inet6_lookup_established(net, &hdr->saddr, th->source,
&hdr->daddr, ntohs(th->dest),
iif, sdif);
- NAPI_GRO_CB(skb)->is_flist = !sk;
+ NAPI_GRO_CB(skb)->is_flist = !sk && !skb_is_gso(skb);
if (sk)
sock_gen_put(sk);
#endif /* IS_ENABLED(CONFIG_IPV6) */