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netfilter: nf_queue: do not release refcouts until nf_reinject is done 

nf_queue is problematic when another NF_QUEUE invocation happens
from nf_reinject().

1. nf_queue is invoked, increments state->sk refcount.
2. skb is queued, waiting for verdict.
3. sk is closed/released.
3. verdict comes back, nf_reinject is called.
4. nf_reinject drops the reference -- refcount can now drop to 0

Instead of get_ref/release_ref pattern, we need to nest the get_ref calls:
    get_ref
       get_ref
       release_ref
     release_ref

So that when we invoke the next processing stage (another netfilter
or the okfn()), we hold at least one reference count on the
devices/socket.

After previous patch, it is now safe to put the entry even after okfn()
has potentially free'd the skb.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2020-03-27 03:24:48 +01:00 committed by Pablo Neira Ayuso
parent 119e52e664
commit af370ab36f
1 changed files with 2 additions and 4 deletions
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6
net/netfilter/nf_queue.c
View File

@ -303,12 +303,10 @@ void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
hooks = nf_hook_entries_head(net, pf, entry->state.hook);
nf_queue_entry_release_refs(entry);
i = entry->hook_index;
if (WARN_ON_ONCE(!hooks || i >= hooks->num_hook_entries)) {
kfree_skb(skb);
kfree(entry);
nf_queue_entry_free(entry);
return;
}
@ -347,6 +345,6 @@ void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
kfree_skb(skb);
}
kfree(entry);
nf_queue_entry_free(entry);
}
EXPORT_SYMBOL(nf_reinject);