If we're being delivered packets from multiple CPUs so quickly that the ring lock is contended for CPU tries, then it's safe to assume that the queue is near capacity anyway, so just drop the packet rather than spinning. This helps deal with multicore DoS that can interfere with data path performance. It _still_ does not completely fix the issue, but it again chips away at it.
Reported-by: Streun Fabio fstreun@student.ethz.ch Cc: stable@vger.kernel.org Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com --- drivers/net/wireguard/receive.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/net/wireguard/receive.c b/drivers/net/wireguard/receive.c index f4e537e3e8ec..7b8df406c773 100644 --- a/drivers/net/wireguard/receive.c +++ b/drivers/net/wireguard/receive.c @@ -554,9 +554,19 @@ void wg_packet_receive(struct wg_device *wg, struct sk_buff *skb) case cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION): case cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE): case cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE): { - int cpu; - if (unlikely(!rng_is_initialized() || - ptr_ring_produce_bh(&wg->handshake_queue.ring, skb))) { + int cpu, ret = -EBUSY; + + if (unlikely(!rng_is_initialized())) + goto drop; + if (atomic_read(&wg->handshake_queue_len) > MAX_QUEUED_INCOMING_HANDSHAKES / 2) { + if (spin_trylock_bh(&wg->handshake_queue.ring.producer_lock)) { + ret = __ptr_ring_produce(&wg->handshake_queue.ring, skb); + spin_unlock_bh(&wg->handshake_queue.ring.producer_lock); + } + } else + ret = ptr_ring_produce_bh(&wg->handshake_queue.ring, skb); + if (ret) { + drop: net_dbg_skb_ratelimited("%s: Dropping handshake packet from %pISpfsc\n", wg->dev->name, skb); goto err;