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authorMaxim Mikityanskiy <maximmi@nvidia.com>2022-04-06 15:41:12 +0300
committerAlexei Starovoitov <ast@kernel.org>2022-04-06 09:44:45 -0700
commit2e8702cc0cfa1080f29fd64003c00a3e24ac38de (patch)
treefd5be61e7dbd7c863e13a6784348eacde24efdb7 /net
parent0a210af6d0a0595fef566e7eeb072f10f37774be (diff)
bpf: Support dual-stack sockets in bpf_tcp_check_syncookie
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> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Tariq Toukan <tariqt@nvidia.com> Acked-by: Arthur Fabre <afabre@cloudflare.com> Link: https://lore.kernel.org/bpf/20220406124113.2795730-1-maximmi@nvidia.com
Diffstat (limited to 'net')
-rw-r--r--net/core/filter.c17
1 files changed, 13 insertions, 4 deletions
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 */