[PATCH 4.19 20/62] tcp: Fix data-races around some timeout sysctl knobs.

[Greg Kroah-Hartman]

From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>

[ Upstream commit 39e24435a776e9de5c6dd188836cf2523547804b ]

While reading these sysctl knobs, they can be changed concurrently.
Thus, we need to add READ_ONCE() to their readers.

  - tcp_retries1
  - tcp_retries2
  - tcp_orphan_retries
  - tcp_fin_timeout

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 include/net/tcp.h     |  3 ++-
 net/ipv4/tcp.c        |  2 +-
 net/ipv4/tcp_output.c |  2 +-
 net/ipv4/tcp_timer.c  | 10 +++++-----
 4 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 5c5807ed66ee..f92b93cf074c 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1430,7 +1430,8 @@ static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
 
 static inline int tcp_fin_time(const struct sock *sk)
 {
-	int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
+	int fin_timeout = tcp_sk(sk)->linger2 ? :
+		READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fin_timeout);
 	const int rto = inet_csk(sk)->icsk_rto;
 
 	if (fin_timeout < (rto << 2) - (rto >> 1))
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b1b121d5076c..0f89d0f2c21f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3386,7 +3386,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
 	case TCP_LINGER2:
 		val = tp->linger2;
 		if (val >= 0)
-			val = (val ? : net->ipv4.sysctl_tcp_fin_timeout) / HZ;
+			val = (val ? : READ_ONCE(net->ipv4.sysctl_tcp_fin_timeout)) / HZ;
 		break;
 	case TCP_DEFER_ACCEPT:
 		val = retrans_to_secs(icsk->icsk_accept_queue.rskq_defer_accept,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 33f9a486661c..3d5ea169e905 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3776,7 +3776,7 @@ void tcp_send_probe0(struct sock *sk)
 	}
 
 	if (err <= 0) {
-		if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
+		if (icsk->icsk_backoff < READ_ONCE(net->ipv4.sysctl_tcp_retries2))
 			icsk->icsk_backoff++;
 		icsk->icsk_probes_out++;
 		probe_max = TCP_RTO_MAX;
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 5d761333ffc4..e905fff09fea 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -124,7 +124,7 @@ static int tcp_out_of_resources(struct sock *sk, bool do_reset)
  */
 static int tcp_orphan_retries(struct sock *sk, bool alive)
 {
-	int retries = sock_net(sk)->ipv4.sysctl_tcp_orphan_retries; /* May be zero. */
+	int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */
 
 	/* We know from an ICMP that something is wrong. */
 	if (sk->sk_err_soft && !alive)
@@ -226,7 +226,7 @@ static int tcp_write_timeout(struct sock *sk)
 		retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries;
 		expired = icsk->icsk_retransmits >= retry_until;
 	} else {
-		if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) {
+		if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) {
 			/* Black hole detection */
 			tcp_mtu_probing(icsk, sk);
 
@@ -235,7 +235,7 @@ static int tcp_write_timeout(struct sock *sk)
 			sk_rethink_txhash(sk);
 		}
 
-		retry_until = net->ipv4.sysctl_tcp_retries2;
+		retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2);
 		if (sock_flag(sk, SOCK_DEAD)) {
 			const bool alive = icsk->icsk_rto < TCP_RTO_MAX;
 
@@ -362,7 +362,7 @@ static void tcp_probe_timer(struct sock *sk)
 		 (s32)(tcp_time_stamp(tp) - start_ts) > icsk->icsk_user_timeout)
 		goto abort;
 
-	max_probes = sock_net(sk)->ipv4.sysctl_tcp_retries2;
+	max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2);
 	if (sock_flag(sk, SOCK_DEAD)) {
 		const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
 
@@ -556,7 +556,7 @@ void tcp_retransmit_timer(struct sock *sk)
 	}
 	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 				  tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX);
-	if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1 + 1, 0))
+	if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0))
 		__sk_dst_reset(sk);
 
 out:;
-- 
2.35.1