From: Eric Dumazet edumazet@google.com
[ Upstream commit b9d83ab8a708f23a4001d60e9d8d0b3be3d9f607 ]
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: d346a3fae3ff ("packet: introduce PACKET_QDISC_BYPASS socket option") Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/packet/af_packet.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 1ab65f7f2a0ae..b5487bd8ffc9d 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -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) @@ -2866,7 +2867,8 @@ 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); @@ -3069,7 +3071,8 @@ 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); @@ -4006,7 +4009,8 @@ 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: