[PATCH 5.18 071/158] tcp: Fix data-races around some timeout sysctl knobs.

Greg Kroah-Hartman
2022-07-27T17:40:05Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ 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@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 e6f9a02fa465..815ea8f9b93f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1541,7 +1541,8 @@ 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 0e0ee9c58257..164603527399 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3994,7 +3994,7 @@ 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 99a2f4518e2e..3f20642c8171 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4088,7 +4088,7 @@ void tcp_send_probe0(struct sock *sk)

icsk->icsk_probes_out++;
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++;
timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
} else {
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index a234704e8163..ec5277becc6a 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -143,7 +143,7 @@ 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)
@@ -243,14 +243,14 @@ static int tcp_write_timeout(struct sock *sk)
READ_ONCE(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);

__dst_negative_advice(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;

@@ -381,7 +381,7 @@ static void tcp_probe_timer(struct sock *sk)
msecs_to_jiffies(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;

@@ -589,7 +589,7 @@ 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