Commit 161642e2 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller

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: default avatarEric Dumazet <>
Cc: Willem de Bruijn <>
Cc: Eric Leblond <>
Signed-off-by: default avatarDavid S. Miller <>
parent 99165967
......@@ -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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