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packet: hold bind lock when rebinding to fanout hook

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Packet socket bind operations must hold the po->bind_lock. This keeps
po->running consistent with whether the socket is actually on a ptype
list to receive packets.

fanout_add unbinds a socket and its packet_rcv/tpacket_rcv call, then
binds the fanout object to receive through packet_rcv_fanout.

Make it hold the po->bind_lock when testing po->running and rebinding.
Else, it can race with other rebind operations, such as that in
packet_set_ring from packet_rcv to tpacket_rcv. Concurrent updates
can result in a socket being added to a fanout group twice, causing
use-after-free KASAN bug reports, among others.

Reported independently by both trinity and syzkaller.
Verified that the syzkaller reproducer passes after this patch.

Fixes: dc99f600698d ("packet: Add fanout support.")
Reported-by: nixioaming <nixiaoming@huawei.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2017-09-14 17:14:41 -04:00 committed by David S. Miller
parent 35e015e1f5
commit 008ba2a13f
1 changed files with 11 additions and 5 deletions
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16
net/packet/af_packet.c
View File

@ -1684,10 +1684,6 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
mutex_lock(&fanout_mutex);
err = -EINVAL;
if (!po->running)
goto out;
err = -EALREADY;
if (po->fanout)
goto out;
@ -1749,7 +1745,10 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
list_add(&match->list, &fanout_list);
}
err = -EINVAL;
if (match->type == type &&
spin_lock(&po->bind_lock);
if (po->running &&
match->type == type &&
match->prot_hook.type == po->prot_hook.type &&
match->prot_hook.dev == po->prot_hook.dev) {
err = -ENOSPC;
@ -1761,6 +1760,13 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
err = 0;
}
}
spin_unlock(&po->bind_lock);
if (err && !refcount_read(&match->sk_ref)) {
list_del(&match->list);
kfree(match);
}
out:
if (err && rollover) {
kfree(rollover);