wireguard: receive: annotate data-race around receiving_counter.counter

Syzkaller with KCSAN identified a data-race issue when accessing
keypair->receiving_counter.counter. Use READ_ONCE() and WRITE_ONCE()
annotations to mark the data race as intentional.

    BUG: KCSAN: data-race in wg_packet_decrypt_worker / wg_packet_rx_poll

    write to 0xffff888107765888 of 8 bytes by interrupt on cpu 0:
     counter_validate drivers/net/wireguard/receive.c:321 [inline]
     wg_packet_rx_poll+0x3ac/0xf00 drivers/net/wireguard/receive.c:461
     __napi_poll+0x60/0x3b0 net/core/dev.c:6536
     napi_poll net/core/dev.c:6605 [inline]
     net_rx_action+0x32b/0x750 net/core/dev.c:6738
     __do_softirq+0xc4/0x279 kernel/softirq.c:553
     do_softirq+0x5e/0x90 kernel/softirq.c:454
     __local_bh_enable_ip+0x64/0x70 kernel/softirq.c:381
     __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:167 [inline]
     _raw_spin_unlock_bh+0x36/0x40 kernel/locking/spinlock.c:210
     spin_unlock_bh include/linux/spinlock.h:396 [inline]
     ptr_ring_consume_bh include/linux/ptr_ring.h:367 [inline]
     wg_packet_decrypt_worker+0x6c5/0x700 drivers/net/wireguard/receive.c:499
     process_one_work kernel/workqueue.c:2633 [inline]
     ...

    read to 0xffff888107765888 of 8 bytes by task 3196 on cpu 1:
     decrypt_packet drivers/net/wireguard/receive.c:252 [inline]
     wg_packet_decrypt_worker+0x220/0x700 drivers/net/wireguard/receive.c:501
     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
     ...

Fixes: a9e90d9931f3 ("wireguard: noise: separate receive counter from send counter")
Reported-by: syzbot+d1de830e4ecdaac83d89@syzkaller.appspotmail.com
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/wireguard/receive.c b/drivers/net/wireguard/receive.c
index df275b4fccb6d01a3bc22bc5bcc418b569a728e5..eb8851113654f5332219ffde63b61c8c470df759 100644 (file)
--- a/drivers/net/wireguard/receive.c
+++ b/drivers/net/wireguard/receive.c
@@ -251,7 +251,7 @@ static bool decrypt_packet(struct sk_buff *skb, struct noise_keypair *keypair)
 
        if (unlikely(!READ_ONCE(keypair->receiving.is_valid) ||
                  wg_birthdate_has_expired(keypair->receiving.birthdate, REJECT_AFTER_TIME) ||
-                 keypair->receiving_counter.counter >= REJECT_AFTER_MESSAGES)) {
+                 READ_ONCE(keypair->receiving_counter.counter) >= REJECT_AFTER_MESSAGES)) {
                WRITE_ONCE(keypair->receiving.is_valid, false);
                return false;
        }
@@ -318,7 +318,7 @@ static bool counter_validate(struct noise_replay_counter *counter, u64 their_cou
                for (i = 1; i <= top; ++i)
                        counter->backtrack[(i + index_current) &
                                ((COUNTER_BITS_TOTAL / BITS_PER_LONG) - 1)] = 0;
-               counter->counter = their_counter;
+               WRITE_ONCE(counter->counter, their_counter);
        }
 
        index &= (COUNTER_BITS_TOTAL / BITS_PER_LONG) - 1;
@@ -463,7 +463,7 @@ int wg_packet_rx_poll(struct napi_struct *napi, int budget)
                        net_dbg_ratelimited("%s: Packet has invalid nonce %llu (max %llu)\n",
                                            peer->device->dev->name,
                                            PACKET_CB(skb)->nonce,
-                                           keypair->receiving_counter.counter);
+                                           READ_ONCE(keypair->receiving_counter.counter));
                        goto next;
                }