From: Florian Westphal <fw@xxxxxxxxx> commit 747670fd9a2d1b7774030dba65ca022ba442ce71 upstream. There is no guarantee that state->sk refers to a full socket. If refcount transitions to 0, sock_put calls sk_free which then ends up with garbage fields. I'd like to thank Oleksandr Natalenko and Jiri Benc for considerable debug work and pointing out state->sk oddities. Fixes: ca6fb0651883 ("tcp: attach SYNACK messages to request sockets instead of listener") Tested-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxx> Signed-off-by: Florian Westphal <fw@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/netfilter/nf_queue.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/net/netfilter/nf_queue.c +++ b/net/netfilter/nf_queue.c @@ -64,6 +64,15 @@ static void nf_queue_entry_release_br_nf #endif } +static void nf_queue_sock_put(struct sock *sk) +{ +#ifdef CONFIG_INET + sock_gen_put(sk); +#else + sock_put(sk); +#endif +} + void nf_queue_entry_release_refs(struct nf_queue_entry *entry) { struct nf_hook_state *state = &entry->state; @@ -74,7 +83,7 @@ void nf_queue_entry_release_refs(struct if (state->out) dev_put(state->out); if (state->sk) - sock_put(state->sk); + nf_queue_sock_put(state->sk); nf_queue_entry_release_br_nf_refs(entry->skb); } Patches currently in stable-queue which might be from fw@xxxxxxxxx are queue-5.4/netfilter-nf_queue-fix-possible-use-after-free.patch queue-5.4/netfilter-fix-use-after-free-in-__nf_register_net_hook.patch queue-5.4/netfilter-nf_queue-don-t-assume-sk-is-full-socket.patch