From: Willem de Bruijn <willemb@xxxxxxxxxx> commit a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab upstream. 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@xxxxxxxxxxxx/ Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.") Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://patch.msgid.link/20241001171752.107580-1-willemdebruijn.kernel@xxxxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/udp_offload.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -290,8 +290,26 @@ 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 those 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; + + uh = udp_hdr(gso_skb); + if (is_ipv6) + uh->check = ~udp_v6_check(gso_skb->len, + &ipv6_hdr(gso_skb)->saddr, + &ipv6_hdr(gso_skb)->daddr, 0); + else + uh->check = ~udp_v4_check(gso_skb->len, + ip_hdr(gso_skb)->saddr, + ip_hdr(gso_skb)->daddr, 0); + } skb_pull(gso_skb, sizeof(*uh)); Patches currently in stable-queue which might be from willemb@xxxxxxxxxx are queue-6.10/net-add-more-sanity-checks-to-qdisc_pkt_len_init.patch queue-6.10/net-gso-fix-tcp-fraglist-segmentation-after-pull-from-frag_list.patch queue-6.10/gso-fix-udp-gso-fraglist-segmentation-after-pull-from-frag_list.patch queue-6.10/net-test-for-not-too-small-csum_start-in-virtio_net_.patch queue-6.10/vrf-revert-vrf-remove-unnecessary-rcu-bh-critical-section.patch queue-6.10/net-avoid-potential-underflow-in-qdisc_pkt_len_init-.patch
