Felix Fietkau wrote: > On 26.09.24 09:19, Willem de Bruijn wrote: > > 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. > > But only if there is no checksum offload, right? Because the way I > implemented it, the lines further below starting with > if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) > will initialize th->check and set ip_summed to CHECKSUM_PARTIAL > Or am I missing something? Oh you're right, __tcp_v4_send_check then does this, so no need to open code it.
