Re: [PATCH net] wireguard: mark racy persistent_keepalive_interval accesses

[Jason A. Donenfeld]

On Sun, Oct 11, 2026 at 05:23:22PM +0700, Nguyen Ngoc Thang wrote:
> wg_set_device_doit() updates peer->persistent_keepalive_interval under
> device_update_lock, while the RX/TX paths read it locklessly in
> wg_timers_any_authenticated_packet_traversal() and in the persistent
> keepalive timer. KCSAN reports the race:
> 
>   BUG: KCSAN: data-race in set_peer / wg_timers_any_authenticated_packet_traversal
> 
>   write to ... by task 3648 on cpu 1:
>    set_peer+0x...  drivers/net/wireguard/netlink.c:457
>    wg_set_device_doit+0x...
>   read to ... by task 3652 on cpu 0:
>    wg_timers_any_authenticated_packet_traversal+0x...  timers.c:217
>    wg_packet_consume_data_done+0x...
>    wg_packet_rx_poll+0x...
> 
> The race is benign, but the reader also loads the field twice, so the
> zero check and the timer expiry computation can see different values.
> Load it once with READ_ONCE() and mark the writer and the other
> lockless reader accordingly.
 
Applied, thank you!