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([2a09:bac5:d45a:16c8::245:79]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2e8422e1643sm31643955ad.70.2026.10.11.03.23.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Oct 2026 03:23:27 -0700 (PDT) From: Nguyen Ngoc Thang To: "Jason A . Donenfeld" , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Andrew Lunn , wireguard@lists.zx2c4.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Nguyen Ngoc Thang , syzbot+de9701a2cad597c14d34@syzkaller.appspotmail.com Subject: [PATCH net] wireguard: mark racy persistent_keepalive_interval accesses Date: Sun, 11 Oct 2026 17:23:22 +0700 Message-ID: <20261011102322.355167-1-ngocthang2710.1999@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Reported-by: syzbot+de9701a2cad597c14d34@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=de9701a2cad597c14d34 Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Nguyen Ngoc Thang --- drivers/net/wireguard/netlink.c | 3 ++- drivers/net/wireguard/timers.c | 8 +++++--- 2 files changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/net/wireguard/netlink.c b/drivers/net/wireguard/netlink.c index 1da7e98d0d50..fafe2900c92b 100644 --- a/drivers/net/wireguard/netlink.c +++ b/drivers/net/wireguard/netlink.c @@ -454,7 +454,8 @@ static int set_peer(struct wg_device *wg, struct nlattr **attrs) persistent_keepalive_interval && netif_running(wg->dev); - peer->persistent_keepalive_interval = persistent_keepalive_interval; + WRITE_ONCE(peer->persistent_keepalive_interval, + persistent_keepalive_interval); if (send_keepalive) wg_packet_send_keepalive(peer); } diff --git a/drivers/net/wireguard/timers.c b/drivers/net/wireguard/timers.c index 4016a3065602..c4697e8522b3 100644 --- a/drivers/net/wireguard/timers.c +++ b/drivers/net/wireguard/timers.c @@ -140,7 +140,7 @@ static void wg_expired_send_persistent_keepalive(struct timer_list *timer) struct wg_peer *peer = timer_container_of(peer, timer, timer_persistent_keepalive); - if (likely(peer->persistent_keepalive_interval)) + if (likely(READ_ONCE(peer->persistent_keepalive_interval))) wg_packet_send_keepalive(peer); } @@ -214,9 +214,11 @@ void wg_timers_session_derived(struct wg_peer *peer) */ void wg_timers_any_authenticated_packet_traversal(struct wg_peer *peer) { - if (peer->persistent_keepalive_interval) + u16 interval = READ_ONCE(peer->persistent_keepalive_interval); + + if (interval) mod_peer_timer(peer, &peer->timer_persistent_keepalive, - jiffies + peer->persistent_keepalive_interval * HZ); + jiffies + interval * HZ); } void wg_timers_init(struct wg_peer *peer) -- 2.43.0