[PATCH 4.19 26/62] tcp: Fix data-races around sysctl_tcp_recovery.

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Kuniyuki Iwashima <kuniyu@amazon.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@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.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 afe195e03a95..731c4d220905 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1938,7 +1938,8 @@ 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 0d96decba13d..61969bb9395c 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;
 	}
 
@@ -203,7 +204,8 @@ 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