netdev - [PATCH] udp: Prevent reuseport_select_sock from reading uninitialized socks

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Date:   Thu,  7 Jan 2021 16:11:10 +1100
From:   Baptiste Lepers <baptiste.lepers@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     davem@...emloft.net, kuba@...nel.org, willemb@...gle.com,
        netdev@...r.kernel.org, baptiste.lepers@...il.com
Subject: [PATCH] udp: Prevent reuseport_select_sock from reading uninitialized socks

reuse->socks[] is modified concurrently by reuseport_add_sock. To
prevent reading values that have not been fully initialized, only read
the array up until the last known safe index instead of incorrectly
re-reading the last index of the array.

Fixes: acdcecc61285f ("udp: correct reuseport selection with connected
sockets")
Signed-off-by: Baptiste Lepers <baptiste.lepers@...il.com>
---
 net/core/sock_reuseport.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index bbdd3c7b6cb5..b065f0a103ed 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -293,7 +293,7 @@ struct sock *reuseport_select_sock(struct sock *sk,
 			i = j = reciprocal_scale(hash, socks);
 			while (reuse->socks[i]->sk_state == TCP_ESTABLISHED) {
 				i++;
-				if (i >= reuse->num_socks)
+				if (i >= socks)
 					i = 0;
 				if (i == j)
 					goto out;
-- 
2.17.1