From 3f36b9a15a069c8f3a315cae6b596588c51fd177 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Thu, 4 Jul 2024 17:45:16 +0200
Subject: [PATCH] wireguard: queueing: annotate intentional data race in cpu
round robin
commit 2fe3d6d2053c57f2eae5e85ca1656d185ebbe4e8 upstream.
KCSAN reports a race in the CPU round robin function, which, as the
comment points out, is intentional:
BUG: KCSAN: data-race in wg_packet_send_staged_packets / wg_packet_send_staged_packets
read to 0xffff88811254eb28 of 4 bytes by task 3160 on cpu 1:
wg_cpumask_next_online drivers/net/wireguard/queueing.h:127 [inline]
wg_queue_enqueue_per_device_and_peer drivers/net/wireguard/queueing.h:173 [inline]
wg_packet_create_data drivers/net/wireguard/send.c:320 [inline]
wg_packet_send_staged_packets+0x60e/0xac0 drivers/net/wireguard/send.c:388
wg_packet_send_keepalive+0xe2/0x100 drivers/net/wireguard/send.c:239
wg_receive_handshake_packet drivers/net/wireguard/receive.c:186 [inline]
wg_packet_handshake_receive_worker+0x449/0x5f0 drivers/net/wireguard/receive.c:213
process_one_work kernel/workqueue.c:3248 [inline]
process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3329
worker_thread+0x526/0x720 kernel/workqueue.c:3409
kthread+0x1d1/0x210 kernel/kthread.c:389
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
write to 0xffff88811254eb28 of 4 bytes by task 3158 on cpu 0:
wg_cpumask_next_online drivers/net/wireguard/queueing.h:130 [inline]
wg_queue_enqueue_per_device_and_peer drivers/net/wireguard/queueing.h:173 [inline]
wg_packet_create_data drivers/net/wireguard/send.c:320 [inline]
wg_packet_send_staged_packets+0x6e5/0xac0 drivers/net/wireguard/send.c:388
wg_packet_send_keepalive+0xe2/0x100 drivers/net/wireguard/send.c:239
wg_receive_handshake_packet drivers/net/wireguard/receive.c:186 [inline]
wg_packet_handshake_receive_worker+0x449/0x5f0 drivers/net/wireguard/receive.c:213
process_one_work kernel/workqueue.c:3248 [inline]
process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3329
worker_thread+0x526/0x720 kernel/workqueue.c:3409
kthread+0x1d1/0x210 kernel/kthread.c:389
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
value changed: 0xffffffff -> 0x00000000
Mark this race as intentional by using READ/WRITE_ONCE().
Cc: stable@vger.kernel.org
Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://patch.msgid.link/20240704154517.1572127-4-Jason@zx2c4.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/wireguard/queueing.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
index a2e702f8c5826..5d2480d90fdb9 100644
--- a/drivers/net/wireguard/queueing.h
+++ b/drivers/net/wireguard/queueing.h
@@ -126,10 +126,10 @@ static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
*/
static inline int wg_cpumask_next_online(int *last_cpu)
{
- int cpu = cpumask_next(*last_cpu, cpu_online_mask);
+ int cpu = cpumask_next(READ_ONCE(*last_cpu), cpu_online_mask);
if (cpu >= nr_cpu_ids)
cpu = cpumask_first(cpu_online_mask);
- *last_cpu = cpu;
+ WRITE_ONCE(*last_cpu, cpu);
return cpu;
}
--
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