tcp: Fix a data-race around sysctl_tcp_retrans_collapse.

[ Upstream commit 1a63cb91f0c2fcdeced6d6edee8d1d886583d139 ]

While reading sysctl_tcp_retrans_collapse, it can be changed
concurrently.  Thus, we need to add READ_ONCE() to its reader.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 94f7841..caf9283 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3108,7 +3108,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
        struct sk_buff *skb = to, *tmp;
        bool first = true;
 
-       if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
+       if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse))
                return;
        if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
                return;