Merge: [9.6 P1] Wireguard: stable backport from upstream

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/5290

JIRA: https://issues.redhat.com/browse/RHEL-60227

```
wireguard: queueing: annotate intentional data race in cpu round robin

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: e7096c1 ("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>
(cherry picked from commit 2fe3d6d)
```
```
wireguard: send: annotate intentional data race in checking empty queue

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: e7096c1 ("net: WireGuard secure network tunnel")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://patch.msgid.link/20240704154517.1572127-5-Jason@zx2c4.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
(cherry picked from commit 381a7d4)
```

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

---

<small>Created 2024-09-26 03:21 UTC by backporter - [KWF FAQ](https://red.ht/kernel_workflow_doc) - [Slack #team-kernel-workflow](https://redhat-internal.slack.com/archives/C04LRUPMJQ5) - [Source](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/webhook/utils/backporter.py) - [Documentation](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/docs/README.backporter.md) - [Report an issue](https://gitlab.com/cki-project/kernel-workflow/-/issues/new?issue%5Btitle%5D=backporter%20webhook%20issue)</small>

Approved-by: Hangbin Liu <haliu@redhat.com>
Approved-by: Florian Westphal <fwestpha@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Rado Vrbovsky <rvrbovsk@redhat.com>

Author: emmil

drivers/net/wireguard/queueing.h

@@ -124,10 +124,10 @@ 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;
 }
 

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))