[PATCH 5.4 77/84] netfilter: nft_socket: only do sk lookups when indev is available

Greg Kroah-Hartman
2022-05-04T16:54:52Z

From: Florian Westphal <fw@strlen.de>

commit 743b83f15d4069ea57c3e40996bf4a1077e0cdc1 upstream.

Check if the incoming interface is available and NFT_BREAK
in case neither skb->sk nor input device are set.

Because nf_sk_lookup_slow*() assume packet headers are in the
'in' direction, use in postrouting is not going to yield a meaningful
result. Same is true for the forward chain, so restrict the use
to prerouting, input and output.

Use in output work if a socket is already attached to the skb.

Fixes: 554ced0a6e29 ("netfilter: nf_tables: add support for native socket matching")
Reported-and-tested-by: Topi Miettinen <toiwoton@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/nft_socket.c | 52 ++++++++++++++++++++++++++++++++-------------
1 file changed, 38 insertions(+), 14 deletions(-)

--- a/net/netfilter/nft_socket.c
+++ b/net/netfilter/nft_socket.c
@@ -14,6 +14,32 @@ struct nft_socket {
};
};

+static struct sock *nft_socket_do_lookup(const struct nft_pktinfo *pkt)
+{
+ const struct net_device *indev = nft_in(pkt);
+ const struct sk_buff *skb = pkt->skb;
+ struct sock *sk = NULL;
+
+ if (!indev)
+ return NULL;
+
+ switch (nft_pf(pkt)) {
+ case NFPROTO_IPV4:
+ sk = nf_sk_lookup_slow_v4(nft_net(pkt), skb, indev);
+ break;
+#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
+ case NFPROTO_IPV6:
+ sk = nf_sk_lookup_slow_v6(nft_net(pkt), skb, indev);
+ break;
+#endif
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
+
+ return sk;
+}
+
static void nft_socket_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
@@ -27,20 +53,7 @@ static void nft_socket_eval(const struct
sk = NULL;

if (!sk)
- switch(nft_pf(pkt)) {
- case NFPROTO_IPV4:
- sk = nf_sk_lookup_slow_v4(nft_net(pkt), skb, nft_in(pkt));
- break;
-#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
- case NFPROTO_IPV6:
- sk = nf_sk_lookup_slow_v6(nft_net(pkt), skb, nft_in(pkt));
- break;
-#endif
- default:
- WARN_ON_ONCE(1);
- regs->verdict.code = NFT_BREAK;
- return;
- }
+ sk = nft_socket_do_lookup(pkt);

if (!sk) {
regs->verdict.code = NFT_BREAK;
@@ -123,6 +136,16 @@ static int nft_socket_dump(struct sk_buf
return 0;
}

+static int nft_socket_validate(const struct nft_ctx *ctx,
+ const struct nft_expr *expr,
+ const struct nft_data **data)
+{
+ return nft_chain_validate_hooks(ctx->chain,
+ (1 << NF_INET_PRE_ROUTING) |
+ (1 << NF_INET_LOCAL_IN) |
+ (1 << NF_INET_LOCAL_OUT));
+}
+
static struct nft_expr_type nft_socket_type;
static const struct nft_expr_ops nft_socket_ops = {
.type = &nft_socket_type,
@@ -130,6 +153,7 @@ static const struct nft_expr_ops nft_soc
.eval = nft_socket_eval,
.init = nft_socket_init,
.dump = nft_socket_dump,
+ .validate = nft_socket_validate,
};

static struct nft_expr_type nft_socket_type __read_mostly = {