linux-kernel - [PATCH 4.9 10/26] tcp/dccp: Fix a data-race around sysctl_tcp_fwmark

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Message-Id: <20220727160959.547072616@linuxfoundation.org>
Date:   Wed, 27 Jul 2022 18:10:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kuniyuki Iwashima <kuniyu@...zon.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 10/26] tcp/dccp: Fix a data-race around sysctl_tcp_fwmark_accept.

From: Kuniyuki Iwashima <kuniyu@...zon.com>

[ Upstream commit 1a0008f9df59451d0a17806c1ee1a19857032fa8 ]

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

Fixes: 84f39b08d786 ("net: support marking accepting TCP sockets")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/net/inet_sock.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index 6213a90a8cec..f5dbee53fb85 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -113,7 +113,8 @@ static inline struct inet_request_sock *inet_rsk(const struct request_sock *sk)
 
 static inline u32 inet_request_mark(const struct sock *sk, struct sk_buff *skb)
 {
-	if (!sk->sk_mark && sock_net(sk)->ipv4.sysctl_tcp_fwmark_accept)
+	if (!sk->sk_mark &&
+	    READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fwmark_accept))
 		return skb->mark;
 
 	return sk->sk_mark;
-- 
2.35.1