Commit 161642e2 authored Oct 09, 2015 by Eric Dumazet Committed by David S. Miller Oct 12, 2015

packet: fix match_fanout_group()



Recent TCP listener patches exposed a prior af_packet bug :
match_fanout_group() blindly assumes it is always safe
to cast sk to a packet socket to compare fanout with af_packet_priv

But SYNACK packets can be sent while attached to request_sock, which
are smaller than a "struct sock".

We can read non existent memory and crash.

Fixes: c0de08d0 ("af_packet: don't emit packet on orig fanout group")
Fixes: ca6fb065 ("tcp: attach SYNACK messages to request sockets instead of listener")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Eric Leblond <eric@regit.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 99165967

net/packet/af_packet.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -1519,10 +1519,10 @@ static void __fanout_unlink(struct sock sk, struct packet_sock po)

		static bool match_fanout_group(struct packet_type ptype, struct sock sk)
		{
		if (ptype->af_packet_priv == (void )((struct packet_sock )sk)->fanout)
		return true;

		if (sk->sk_family != PF_PACKET)
		return false;

		return ptype->af_packet_priv == pkt_sk(sk)->fanout;
		}

		static void fanout_init_data(struct packet_fanout *f)

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