From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Mon, 18 Jul 2022 17:26:50 +0000 (-0700)
Subject: tcp: Fix a data-race around sysctl_tcp_stdurg.
X-Git-Tag: v5.10.134~30
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=03bb3892f3f18fd98717aa6763ab3885416e69d0;p=users%2Fdwmw2%2Flinux.git

tcp: Fix a data-race around sysctl_tcp_stdurg.

[ Upstream commit 4e08ed41cb1194009fc1a916a59ce3ed4afd77cd ]

While reading sysctl_tcp_stdurg, 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_input.c b/net/ipv4/tcp_input.c
index 1dc1d62093b31..c89452761b3f8 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5492,7 +5492,7 @@ static void tcp_check_urg(struct sock *sk, const struct tcphdr *th)
 	struct tcp_sock *tp = tcp_sk(sk);
 	u32 ptr = ntohs(th->urg_ptr);
 
-	if (ptr && !sock_net(sk)->ipv4.sysctl_tcp_stdurg)
+	if (ptr && !READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_stdurg))
 		ptr--;
 	ptr += ntohl(th->seq);