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Code Issues

kernel: fix crashes after linearizing fraglist GSO skbs

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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>
This commit is contained in:
Felix Fietkau 2024-09-26 10:58:44 +02:00
parent 384d079fd8
commit 774badd8a8
2 changed files with 127 additions and 0 deletions
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53
target/linux/generic/pending-6.6/684-gso-fix-gso-fraglist-segmentation-after-pull-from-fr.patch Normal file
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@ -0,0 +1,53 @@
From: Willem de Bruijn <willemb@google.com>
Date: Sun, 22 Sep 2024 11:03:45 -0400
Subject: [PATCH] gso: fix gso fraglist segmentation after pull from
frag_list
Detect 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 UDP, this
causes a NULL ptr deref in __udpv4_gso_segment_list_csum at
udp_hdr(seg->next)->dest.
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.
Link: https://lore.kernel.org/netdev/20240428142913.18666-1-shiming.cheng@mediatek.com/
Fixes: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Cc: stable@vger.kernel.org
---
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -296,8 +296,16 @@ struct sk_buff *__udp_gso_segment(struct
return NULL;
}
- if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
- return __udp_gso_segment_list(gso_skb, features, is_ipv6);
+ if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST) {
+ /* Detect modified geometry and pass these to skb_segment. */
+ if (skb_pagelen(gso_skb) - sizeof(*uh) == skb_shinfo(gso_skb)->gso_size)
+ return __udp_gso_segment_list(gso_skb, features, is_ipv6);
+
+ /* Setup csum, as fraglist skips this in udp4_gro_receive. */
+ gso_skb->csum_start = skb_transport_header(gso_skb) - gso_skb->head;
+ gso_skb->csum_offset = offsetof(struct udphdr, check);
+ gso_skb->ip_summed = CHECKSUM_PARTIAL;
+ }
skb_pull(gso_skb, sizeof(*uh));

74
target/linux/generic/pending-6.6/685-net-gso-fix-tcp-fraglist-segmentation-after-pull-fro.patch Normal file
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From: Felix Fietkau <nbd@nbd.name>
Date: Thu, 26 Sep 2024 10:41:30 +0200
Subject: [PATCH] net: gso: fix tcp fraglist segmentation after pull from
frag_list
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
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -101,8 +101,14 @@ 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
@@ -158,8 +158,14 @@ 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);