linux-kernel - [PATCH 5.4 45/87] udp: Fix a data-race around sysctl_udp_l3mdev

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Message-Id: <20220727161010.877370593@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 5.4 45/87] udp: Fix a data-race around sysctl_udp_l3mdev_accept.

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

[ Upstream commit 3d72bb4188c708bb16758c60822fc4dda7a95174 ]

While reading sysctl_udp_l3mdev_accept, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 63a6fff353d0 ("net: Avoid receiving packets with an l3mdev on unbound UDP 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/udp.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/udp.h b/include/net/udp.h
index 9787a42f7ed3..e66854e767dc 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -252,7 +252,7 @@ static inline bool udp_sk_bound_dev_eq(struct net *net, int bound_dev_if,
 				       int dif, int sdif)
 {
 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
-	return inet_bound_dev_eq(!!net->ipv4.sysctl_udp_l3mdev_accept,
+	return inet_bound_dev_eq(!!READ_ONCE(net->ipv4.sysctl_udp_l3mdev_accept),
 				 bound_dev_if, dif, sdif);
 #else
 	return inet_bound_dev_eq(true, bound_dev_if, dif, sdif);
-- 
2.35.1