Felix Fietkau wrote: > On 25.09.24 22:59, 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. > > Actually, here is something even simpler that should work for both v4 > and v6: Makes sense. It does come with higher cost of calling skb_checksum. > --- > --- a/net/ipv4/tcp_offload.c > +++ b/net/ipv4/tcp_offload.c > @@ -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); > --- a/net/ipv6/tcpv6_offload.c > +++ b/net/ipv6/tcpv6_offload.c > @@ -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); > >
