| Message ID | 20220406124113.2795730-1-maximmi@nvidia.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 2e8702cc0cfa1080f29fd64003c00a3e24ac38de |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf,v5,1/2] bpf: Support dual-stack sockets in bpf_tcp_check_syncookie | expand |
Hello: This series was applied to bpf/bpf.git (master) by Alexei Starovoitov <ast@kernel.org>: On Wed, 6 Apr 2022 15:41:12 +0300 you wrote: > bpf_tcp_gen_syncookie looks at the IP version in the IP header and > validates the address family of the socket. It supports IPv4 packets in > AF_INET6 dual-stack sockets. > > On the other hand, bpf_tcp_check_syncookie looks only at the address > family of the socket, ignoring the real IP version in headers, and > validates only the packet size. This implementation has some drawbacks: > > [...] Here is the summary with links: - [bpf,v5,1/2] bpf: Support dual-stack sockets in bpf_tcp_check_syncookie https://git.kernel.org/bpf/bpf/c/2e8702cc0cfa - [bpf,v5,2/2] bpf: Adjust bpf_tcp_check_syncookie selftest to test dual-stack sockets https://git.kernel.org/bpf/bpf/c/53968dafc4a6 You are awesome, thank you!
diff --git a/net/core/filter.c b/net/core/filter.c index a7044e98765e..64470a727ef7 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -7016,24 +7016,33 @@ BPF_CALL_5(bpf_tcp_check_syncookie, struct sock *, sk, void *, iph, u32, iph_len if (!th->ack || th->rst || th->syn) return -ENOENT; + if (unlikely(iph_len < sizeof(struct iphdr))) + return -EINVAL; + if (tcp_synq_no_recent_overflow(sk)) return -ENOENT; cookie = ntohl(th->ack_seq) - 1; - switch (sk->sk_family) { - case AF_INET: - if (unlikely(iph_len < sizeof(struct iphdr))) + /* Both struct iphdr and struct ipv6hdr have the version field at the + * same offset so we can cast to the shorter header (struct iphdr). + */ + switch (((struct iphdr *)iph)->version) { + case 4: + if (sk->sk_family == AF_INET6 && ipv6_only_sock(sk)) return -EINVAL; ret = __cookie_v4_check((struct iphdr *)iph, th, cookie); break; #if IS_BUILTIN(CONFIG_IPV6) - case AF_INET6: + case 6: if (unlikely(iph_len < sizeof(struct ipv6hdr))) return -EINVAL; + if (sk->sk_family != AF_INET6) + return -EINVAL; + ret = __cookie_v6_check((struct ipv6hdr *)iph, th, cookie); break; #endif /* CONFIG_IPV6 */
bpf_tcp_gen_syncookie looks at the IP version in the IP header and validates the address family of the socket. It supports IPv4 packets in AF_INET6 dual-stack sockets. On the other hand, bpf_tcp_check_syncookie looks only at the address family of the socket, ignoring the real IP version in headers, and validates only the packet size. This implementation has some drawbacks: 1. Packets are not validated properly, allowing a BPF program to trick bpf_tcp_check_syncookie into handling an IPv6 packet on an IPv4 socket. 2. Dual-stack sockets fail the checks on IPv4 packets. IPv4 clients end up receiving a SYNACK with the cookie, but the following ACK gets dropped. This patch fixes these issues by changing the checks in bpf_tcp_check_syncookie to match the ones in bpf_tcp_gen_syncookie. IP version from the header is taken into account, and it is validated properly with address family. Fixes: 399040847084 ("bpf: add helper to check for a valid SYN cookie") Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com> Reviewed-by: Tariq Toukan <tariqt@nvidia.com> Acked-by: Arthur Fabre <afabre@cloudflare.com> --- net/core/filter.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)