udp: Prevent reuseport_select_sock from reading uninitialized socks

BLepers · kuba-moo · commit fd2ddef04359 · 2021-01-08T19:15:40.000-08:00
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: acdcecc ("udp: correct reuseport selection with connected sockets") Signed-off-by: Baptiste Lepers <baptiste.lepers@gmail.com> Acked-by: Willem de Bruijn <willemb@google.com> Link: https://lore.kernel.org/r/20210107051110.12247-1-baptiste.lepers@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git 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;
