Felix Fietkau wrote: > On 25.09.24 21:09, Willem de Bruijn wrote: > > Felix Fietkau wrote: > >> On 22.09.24 17:03, Willem de Bruijn wrote: > >> > From: Willem de Bruijn <willemb@xxxxxxxxxx> > >> > > >> > 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: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.") > >> > Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx> > >> > Cc: stable@xxxxxxxxxxxxxxx > >> > > >> > --- > >> > diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c > >> > index d842303587af..e457fa9143a6 100644 > >> > --- a/net/ipv4/udp_offload.c > >> > +++ b/net/ipv4/udp_offload.c > >> > @@ -296,8 +296,16 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb, > >> > 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; > >> > >> I also noticed this uh->check update done by udp4_gro_complete only in > >> case of non-fraglist GRO: > >> > >> if (uh->check) > >> uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr, > >> iph->daddr, 0); > >> > >> I didn't see any equivalent in your patch. Is it missing or left out > >> intentionally? > > > > Thanks. That was not intentional. I think you're right. Am a bit > > concerned that all this testing did not catch it. Perhaps because > > CHECKSUM_PARTIAL looped to ingress on the same machine is simply > > interpreted as CHECKSUM_UNNECESSARY. Need to look into that. > > > > If respinning this, I should also change the Fixes to > > > > Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.") > > > > Analogous to the eventual TCP fix to > > > > Fixes: bee88cd5bd83 ("net: add support for segmenting TCP fraglist GSO packets") > > In the mean time, I've been working on the TCP side. I managed to > reproduce the issue on one of my devices by routing traffic from > Ethernet to Wifi using your BPF test program. > > The following patch makes it work for me for TCP v4. Still need to > test and fix v6. > > - Felix > > --- > --- a/net/ipv4/tcp_offload.c > +++ b/net/ipv4/tcp_offload.c > @@ -101,8 +101,20 @@ 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); > + const struct iphdr *iph; > + > + if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size) > + return __tcp4_gso_segment_list(skb, features); > + > + iph = ip_hdr(skb); > + skb_shinfo(skb)->gso_type &= ~SKB_GSO_FRAGLIST; I left this out, because skb_segment does not care about this bit. > + skb->csum_start = (unsigned char *)th - skb->head; > + skb->csum_offset = offsetof(struct tcphdr, check); > + skb->ip_summed = CHECKSUM_PARTIAL; > + th->check = ~tcp_v4_check(skb->len, iph->saddr, iph->daddr, 0); > + } > > if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) { > const struct iphdr *iph = ip_hdr(skb); >
