This is a note to let you know that I've just added the patch titled
net: fix wrong network header length
to the 5.15-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-fix-wrong-network-header-length.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 522c47125e95fd82472978fcd46295fc96db24e4
Author: Lina Wang <lina.wang@xxxxxxxxxxxx>
Date: Thu May 5 13:48:49 2022 +0800
net: fix wrong network header length
[ Upstream commit cf3ab8d4a797960b4be20565abb3bcd227b18a68 ]
When clatd starts with ebpf offloaing, and NETIF_F_GRO_FRAGLIST is enable,
several skbs are gathered in skb_shinfo(skb)->frag_list. The first skb's
ipv6 header will be changed to ipv4 after bpf_skb_proto_6_to_4,
network_header\transport_header\mac_header have been updated as ipv4 acts,
but other skbs in frag_list didnot update anything, just ipv6 packets.
udp_queue_rcv_skb will call skb_segment_list to traverse other skbs in
frag_list and make sure right udp payload is delivered to user space.
Unfortunately, other skbs in frag_list who are still ipv6 packets are
updated like the first skb and will have wrong transport header length.
e.g.before bpf_skb_proto_6_to_4,the first skb and other skbs in frag_list
has the same network_header(24)& transport_header(64), after
bpf_skb_proto_6_to_4, ipv6 protocol has been changed to ipv4, the first
skb's network_header is 44,transport_header is 64, other skbs in frag_list
didnot change.After skb_segment_list, the other skbs in frag_list has
different network_header(24) and transport_header(44), so there will be 20
bytes different from original,that is difference between ipv6 header and
ipv4 header. Just change transport_header to be the same with original.
Actually, there are two solutions to fix it, one is traversing all skbs
and changing every skb header in bpf_skb_proto_6_to_4, the other is
modifying frag_list skb's header in skb_segment_list. Considering
efficiency, adopt the second one--- when the first skb and other skbs in
frag_list has different network_header length, restore them to make sure
right udp payload is delivered to user space.
Signed-off-by: Lina Wang <lina.wang@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index e4badc189e37..7ef0f5a8ab03 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3873,7 +3873,7 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
unsigned int delta_len = 0;
struct sk_buff *tail = NULL;
struct sk_buff *nskb, *tmp;
- int err;
+ int len_diff, err;
skb_push(skb, -skb_network_offset(skb) + offset);
@@ -3913,9 +3913,11 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
skb_push(nskb, -skb_network_offset(nskb) + offset);
skb_release_head_state(nskb);
+ len_diff = skb_network_header_len(nskb) - skb_network_header_len(skb);
__copy_skb_header(nskb, skb);
skb_headers_offset_update(nskb, skb_headroom(nskb) - skb_headroom(skb));
+ nskb->transport_header += len_diff;
skb_copy_from_linear_data_offset(skb, -tnl_hlen,
nskb->data - tnl_hlen,
offset + tnl_hlen);
