Commit b9d83ab8 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net/packet: annotate accesses to po->xmit 



po->xmit can be set from setsockopt(PACKET_QDISC_BYPASS),
while read locklessly.

Use READ_ONCE()/WRITE_ONCE() to avoid potential load/store
tearing issues.

Fixes: d346a3fa ("packet: introduce PACKET_QDISC_BYPASS socket option")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dc021e6c

net/packet/af_packet.c

+8 −4
Original line number Diff line number Diff line
@@ -307,7 +307,8 @@ static void packet_cached_dev_reset(struct packet_sock *po) 


static bool packet_use_direct_xmit(const struct packet_sock *po)

{

	return po->xmit == packet_direct_xmit;

	/* Paired with WRITE_ONCE() in packet_setsockopt() */

	return READ_ONCE(po->xmit) == packet_direct_xmit;

}



static u16 packet_pick_tx_queue(struct sk_buff *skb)
@@ -2867,7 +2868,8 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) 
		packet_inc_pending(&po->tx_ring);



		status = TP_STATUS_SEND_REQUEST;

		err = po->xmit(skb);

		/* Paired with WRITE_ONCE() in packet_setsockopt() */

		err = READ_ONCE(po->xmit)(skb);

		if (unlikely(err != 0)) {

			if (err > 0)

				err = net_xmit_errno(err);
@@ -3070,7 +3072,8 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) 
		virtio_net_hdr_set_proto(skb, &vnet_hdr);

	}



	err = po->xmit(skb);

	/* Paired with WRITE_ONCE() in packet_setsockopt() */

	err = READ_ONCE(po->xmit)(skb);

	if (unlikely(err != 0)) {

		if (err > 0)

			err = net_xmit_errno(err);
@@ -4007,7 +4010,8 @@ packet_setsockopt(struct socket *sock, int level, int optname, sockptr_t optval, 
		if (copy_from_sockptr(&val, optval, sizeof(val)))

			return -EFAULT;



		po->xmit = val ? packet_direct_xmit : dev_queue_xmit;

		/* Paired with all lockless reads of po->xmit */

		WRITE_ONCE(po->xmit, val ? packet_direct_xmit : dev_queue_xmit);

		return 0;

	}

	default: