KCSAN reports a race in wg_packet_send_keepalive, which is intentional:

BUG: KCSAN: data-race in wg_packet_send_keepalive / wg_packet_send_staged_packets

write to 0xffff88814cd91280 of 8 bytes by task 3194 on cpu 0: __skb_queue_head_init include/linux/skbuff.h:2162 [inline] skb_queue_splice_init include/linux/skbuff.h:2248 [inline] wg_packet_send_staged_packets+0xe5/0xad0 drivers/net/wireguard/send.c:351 wg_xmit+0x5b8/0x660 drivers/net/wireguard/device.c:218 __netdev_start_xmit include/linux/netdevice.h:4940 [inline] netdev_start_xmit include/linux/netdevice.h:4954 [inline] xmit_one net/core/dev.c:3548 [inline] dev_hard_start_xmit+0x11b/0x3f0 net/core/dev.c:3564 __dev_queue_xmit+0xeff/0x1d80 net/core/dev.c:4349 dev_queue_xmit include/linux/netdevice.h:3134 [inline] neigh_connected_output+0x231/0x2a0 net/core/neighbour.c:1592 neigh_output include/net/neighbour.h:542 [inline] ip6_finish_output2+0xa66/0xce0 net/ipv6/ip6_output.c:137 ip6_finish_output+0x1a5/0x490 net/ipv6/ip6_output.c:222 NF_HOOK_COND include/linux/netfilter.h:303 [inline] ip6_output+0xeb/0x220 net/ipv6/ip6_output.c:243 dst_output include/net/dst.h:451 [inline] NF_HOOK include/linux/netfilter.h:314 [inline] ndisc_send_skb+0x4a2/0x670 net/ipv6/ndisc.c:509 ndisc_send_rs+0x3ab/0x3e0 net/ipv6/ndisc.c:719 addrconf_dad_completed+0x640/0x8e0 net/ipv6/addrconf.c:4295 addrconf_dad_work+0x891/0xbc0 process_one_work kernel/workqueue.c:2633 [inline] process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2706 worker_thread+0x525/0x730 kernel/workqueue.c:2787 kthread+0x1d7/0x210 kernel/kthread.c:388 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

read to 0xffff88814cd91280 of 8 bytes by task 3202 on cpu 1: skb_queue_empty include/linux/skbuff.h:1798 [inline] wg_packet_send_keepalive+0x20/0x100 drivers/net/wireguard/send.c:225 wg_receive_handshake_packet drivers/net/wireguard/receive.c:186 [inline] wg_packet_handshake_receive_worker+0x445/0x5e0 drivers/net/wireguard/receive.c:213 process_one_work kernel/workqueue.c:2633 [inline] process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2706 worker_thread+0x525/0x730 kernel/workqueue.c:2787 kthread+0x1d7/0x210 kernel/kthread.c:388 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

value changed: 0xffff888148fef200 -> 0xffff88814cd91280

Mark this race as intentional by using the skb_queue_empty_lockless() function rather than skb_queue_empty(), which uses READ_ONCE() internally to annotate the race.

Cc: stable@vger.kernel.org Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com --- drivers/net/wireguard/send.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireguard/send.c b/drivers/net/wireguard/send.c index 0d48e0f4a1ba..26e09c30d596 100644 --- a/drivers/net/wireguard/send.c +++ b/drivers/net/wireguard/send.c @@ -222,7 +222,7 @@ void wg_packet_send_keepalive(struct wg_peer *peer) { struct sk_buff *skb;

- if (skb_queue_empty(&peer->staged_packet_queue)) { + if (skb_queue_empty_lockless(&peer->staged_packet_queue)) { skb = alloc_skb(DATA_PACKET_HEAD_ROOM + MESSAGE_MINIMUM_LENGTH, GFP_ATOMIC); if (unlikely(!skb))