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netfilter: nf_queue: handle socket prefetch

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In case someone combines bpf socket assign and nf_queue, then we will
queue an skb who references a struct sock that did not have its
reference count incremented.

As we leave rcu protection, there is no guarantee that skb->sk is still
valid.

For refcount-less skb->sk case, try to increment the reference count
and then override the destructor.

In case of failure we have two choices: orphan the skb and 'delete'
preselect or let nf_queue() drop the packet.

Do the latter, it should not happen during normal operation.

Fixes: cf7fbe660f ("bpf: Add socket assign support")
Acked-by: Joe Stringer <joe@cilium.io>
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
Florian Westphal 2022-03-01 00:46:19 +01:00
parent c387307024
commit 3b836da408
1 changed files with 12 additions and 0 deletions
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12
net/netfilter/nf_queue.c
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@ -180,6 +180,18 @@ static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
break;
}
if (skb_sk_is_prefetched(skb)) {
struct sock *sk = skb->sk;
if (!sk_is_refcounted(sk)) {
if (!refcount_inc_not_zero(&sk->sk_refcnt))
return -ENOTCONN;
/* drop refcount on skb_orphan */
skb->destructor = sock_edemux;
}
}
entry = kmalloc(sizeof(*entry) + route_key_size, GFP_ATOMIC);
if (!entry)
return -ENOMEM;