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

Greg Kroah-Hartman
2022-07-27T16:36:47Z

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 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