linux-kernel - [PATCH 4.9 09/26] ip: Fix a data-race around sysctl_fwmark

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Message-Id: <20220727160959.512108187@linuxfoundation.org>
Date:   Wed, 27 Jul 2022 18:10:38 +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 09/26] ip: Fix a data-race around sysctl_fwmark_reflect.

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

[ Upstream commit 85d0b4dbd74b95cc492b1f4e34497d3f894f5d9a ]

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

Fixes: e110861f8609 ("net: add a sysctl to reflect the fwmark on replies")
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/ip.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index c762fd047ef4..f0e13a256582 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -283,7 +283,7 @@ void ipfrag_init(void);
 void ip_static_sysctl_init(void);
 
 #define IP4_REPLY_MARK(net, mark) \
-	((net)->ipv4.sysctl_fwmark_reflect ? (mark) : 0)
+	(READ_ONCE((net)->ipv4.sysctl_fwmark_reflect) ? (mark) : 0)
 
 static inline bool ip_is_fragment(const struct iphdr *iph)
 {
-- 
2.35.1