On 2/18/21, Willem de Bruijn <willemdebruijn.ker...@gmail.com> wrote: > 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. >
Bingo! Nice eye! I confirmed the crash by just memsetting 0x41 to cb before the call. Clearly this should be zeroed by icmp_ndo_xmit. Will send a patch for icmp_ndo_xmit momentarily and will CC you. Jason
