From 58877430836b89115e0e958ca368f3347bce04c8 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Mon, 29 Nov 2021 10:39:27 -0500 Subject: wireguard: receive: drop handshakes if queue lock is contended commit fb32f4f606c17b869805d7cede8b03d78339b50a upstream. 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 Fixes: a8f1bc7bdea3 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld Signed-off-by: Jakub Kicinski Signed-off-by: Jason A. Donenfeld --- 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 f4e537e..7b8df40 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; -- cgit v1.2.3