On Wed, Feb 17, 2021 at 5:56 PM Jason A. Donenfeld <ja...@zx2c4.com> wrote: > > Hi Willem, > > On Wed, Feb 17, 2021 at 11:27 PM Willem de Bruijn > <willemdebruijn.ker...@gmail.com> wrote: > > A vmlinux image might help. I couldn't find one for this kernel. > > https://data.zx2c4.com/icmp_send-crash-e03b4a42-706a-43bf-bc40-1f15966b3216.tar.xz > has .debs with vmlinuz in there, which you can extract to vmlinux, as > well as my own vmlinux elf construction with the symbols added back in > by extracting them from kallsyms. That's the best I've been able to > do, as all of this is coming from somebody random emailing me. > > > But could it be > > that the forwarded packet is not sensible IPv4? The skb->protocol is > > inferred in wg_packet_consume_data_done->ip_tunnel_parse_protocol. > > The wg calls to icmp_ndo_send are gated by checking skb->protocol: > > if (skb->protocol == htons(ETH_P_IP)) > icmp_ndo_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0); > else if (skb->protocol == htons(ETH_P_IPV6)) > icmpv6_ndo_send(skb, ICMPV6_DEST_UNREACH, > ICMPV6_ADDR_UNREACH, 0); > > On the other hand, that code is hit on an error path when > wg_check_packet_protocol returns false: > > static inline bool wg_check_packet_protocol(struct sk_buff *skb) > { > __be16 real_protocol = ip_tunnel_parse_protocol(skb); > return real_protocol && skb->protocol == real_protocol; > } > > So that means, at least in theory, icmp_ndo_send could be called with > skb->protocol != ip_tunnel_parse_protocol(skb). I guess I can address > that. But... is it actually a problem?
For this forwarded packet that arrived on a wireguard tunnel, skb->protocol was originally also set by ip_tunnel_parse_protocol. So likely not. The other issue seems more like a real bug. wg_xmit calling icmp_ndo_send without clearing IPCB first.
