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This fixes some corner cases triggered by enabling fraglist GRO, where some protocols may accidentally or intentionally linearize fraglist skbs. Previously, these skbs became unusable and segmenting them led to crashes. With this patch, they are properly handled by passing them to skb_segment instead of skb_segment_list. Signed-off-by: Felix Fietkau <nbd@nbd.name>
75 lines
2.7 KiB
Diff
75 lines
2.7 KiB
Diff
From: Felix Fietkau <nbd@nbd.name>
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Date: Thu, 26 Sep 2024 10:41:30 +0200
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Subject: [PATCH] net: gso: fix tcp fraglist segmentation after pull from
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frag_list
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Detect tcp gso fraglist skbs with corrupted geometry (see below) and
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pass these to skb_segment instead of skb_segment_list, as the first
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can segment them correctly.
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Valid SKB_GSO_FRAGLIST skbs
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- consist of two or more segments
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- the head_skb holds the protocol headers plus first gso_size
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- one or more frag_list skbs hold exactly one segment
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- all but the last must be gso_size
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Optional datapath hooks such as NAT and BPF (bpf_skb_pull_data) can
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modify these skbs, breaking these invariants.
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In extreme cases they pull all data into skb linear. For TCP, this
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causes a NULL ptr deref in __tcpv4_gso_segment_list_csum at
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tcp_hdr(seg->next).
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Detect invalid geometry due to pull, by checking head_skb size.
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Don't just drop, as this may blackhole a destination. Convert to be
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able to pass to regular skb_segment.
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Approach and description based on a patch by Willem de Bruijn.
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Link: https://lore.kernel.org/netdev/20240428142913.18666-1-shiming.cheng@mediatek.com/
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Link: https://lore.kernel.org/netdev/20240922150450.3873767-1-willemdebruijn.kernel@gmail.com/
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Fixes: bee88cd5bd83 ("net: add support for segmenting TCP fraglist GSO packets")
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Cc: stable@vger.kernel.org
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Cc: Willem de Bruijn <willemb@google.com>
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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---
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--- a/net/ipv4/tcp_offload.c
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+++ b/net/ipv4/tcp_offload.c
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@@ -101,8 +101,14 @@ static struct sk_buff *tcp4_gso_segment(
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if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
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return ERR_PTR(-EINVAL);
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- if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST)
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- return __tcp4_gso_segment_list(skb, features);
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+ if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
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+ struct tcphdr *th = tcp_hdr(skb);
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+
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+ if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size)
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+ return __tcp4_gso_segment_list(skb, features);
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+
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+ skb->ip_summed = CHECKSUM_NONE;
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+ }
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if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
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const struct iphdr *iph = ip_hdr(skb);
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--- a/net/ipv6/tcpv6_offload.c
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+++ b/net/ipv6/tcpv6_offload.c
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@@ -158,8 +158,14 @@ static struct sk_buff *tcp6_gso_segment(
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if (!pskb_may_pull(skb, sizeof(*th)))
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return ERR_PTR(-EINVAL);
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- if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST)
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- return __tcp6_gso_segment_list(skb, features);
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+ if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
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+ struct tcphdr *th = tcp_hdr(skb);
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+
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+ if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size)
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+ return __tcp6_gso_segment_list(skb, features);
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+
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+ skb->ip_summed = CHECKSUM_NONE;
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+ }
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if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
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const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
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