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packet: fix race condition in packet_set_ring

When packet_set_ring creates a ring buffer it will initialize a
struct timer_list if the packet version is TPACKET_V3. This value
can then be raced by a different thread calling setsockopt to
set the version to TPACKET_V1 before packet_set_ring has finished.

This leads to a use-after-free on a function pointer in the
struct timer_list when the socket is closed as the previously
initialized timer will not be deleted.

The bug is fixed by taking lock_sock(sk) in packet_setsockopt when
changing the packet version while also taking the lock at the start
of packet_set_ring.

Change-Id: Iec8b20f499134e1edd0f9214aa4dde477d1674e1
Fixes: f6fb8f1 ("af-packet: TPACKET_V3 flexible buffer implementation.")
Signed-off-by: Philip Pettersson <philip.pettersson@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Philip Pettersson authored and andi34 committed Nov 30, 2016
1 parent d3b0899 commit e798e09deec889662367ad4a0574bd7c9a9161c9
Showing with 13 additions and 8 deletions.
  1. +13 −8 net/packet/af_packet.c
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@@ -2014,18 +2014,24 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
if (optlen != sizeof(val))
return -EINVAL;
if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
return -EBUSY;
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;
switch (val) {
case TPACKET_V1:
case TPACKET_V2:
po->tp_version = val;
return 0;
break;
default:
return -EINVAL;
}
lock_sock(sk);
if (po->rx_ring.pg_vec || po->tx_ring.pg_vec) {
ret = -EBUSY;
} else {
po->tp_version = val;
ret = 0;
}
release_sock(sk);
return ret;
}
case PACKET_RESERVE:
{
@@ -2463,6 +2469,8 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req,
rb = tx_ring ? &po->tx_ring : &po->rx_ring;
rb_queue = tx_ring ? &sk->sk_write_queue : &sk->sk_receive_queue;
lock_sock(sk);
err = -EBUSY;
if (!closing) {
if (atomic_read(&po->mapped))
@@ -2517,8 +2525,6 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req,
goto out;
}
lock_sock(sk);
/* Detach socket from network */
spin_lock(&po->bind_lock);
was_running = po->running;
@@ -2566,11 +2572,10 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req,
}
spin_unlock(&po->bind_lock);
release_sock(sk);
if (pg_vec)
free_pg_vec(pg_vec, order, req->tp_block_nr);
out:
release_sock(sk);
return err;
}

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