linux-kernel - [PATCH 5.4 48/87] tcp: Fix data-races around sysctl_tcp

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Message-Id: <20220727161010.995412934@linuxfoundation.org>
Date:   Wed, 27 Jul 2022 18:10:41 +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 48/87] tcp: Fix data-races around sysctl_tcp_recovery.

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

[ Upstream commit e7d2ef837e14a971a05f60ea08c47f3fed1a36e4 ]

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

Fixes: 4f41b1c58a32 ("tcp: use RACK to detect losses")
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>
---
 net/ipv4/tcp_input.c    | 3 ++-
 net/ipv4/tcp_recovery.c | 6 ++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 28df6c3feb3f..2f57c365ebd5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1950,7 +1950,8 @@ static inline void tcp_init_undo(struct tcp_sock *tp)
 
 static bool tcp_is_rack(const struct sock *sk)
 {
-	return sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION;
+	return READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
+		TCP_RACK_LOSS_DETECTION;
 }
 
 /* If we detect SACK reneging, forget all SACK information
diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
index 8757bb6cb1d9..22ec8dcc1428 100644
--- a/net/ipv4/tcp_recovery.c
+++ b/net/ipv4/tcp_recovery.c
@@ -33,7 +33,8 @@ static u32 tcp_rack_reo_wnd(const struct sock *sk)
 			return 0;
 
 		if (tp->sacked_out >= tp->reordering &&
-		    !(sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_NO_DUPTHRESH))
+		    !(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
+		      TCP_RACK_NO_DUPTHRESH))
 			return 0;
 	}
 
@@ -204,7 +205,8 @@ void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
-	if (sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_STATIC_REO_WND ||
+	if ((READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
+	     TCP_RACK_STATIC_REO_WND) ||
 	    !rs->prior_delivered)
 		return;
 
-- 
2.35.1