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

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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: bee88cd5bd ("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>
This commit is contained in:
Felix Fietkau 2024-09-26 10:53:14 +02:00 committed by Jakub Kicinski
parent 854e9bf5c5
commit 17bd3bd82f
2 changed files with 16 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
net/ipv4/tcp_offload.c
View File

@ -101,8 +101,14 @@ static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
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);

10
net/ipv6/tcpv6_offload.c
View File

@ -159,8 +159,14 @@ static struct sk_buff *tcp6_gso_segment(struct sk_buff *skb,
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);