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tcp: Fix data-races around sysctl_tcp_syn(ack)?_retries.

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While reading sysctl_tcp_syn(ack)?_retries, they can be changed
concurrently.  Thus, we need to add READ_ONCE() to their readers.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kuniyuki Iwashima 2022-07-15 10:17:46 -07:00 committed by David S. Miller
parent f2f316e287
commit 20a3b1c0f6
3 changed files with 11 additions and 5 deletions
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3
net/ipv4/inet_connection_sock.c
View File

@ -833,7 +833,8 @@ static void reqsk_timer_handler(struct timer_list *t)
icsk = inet_csk(sk_listener); icsk = inet_csk(sk_listener);
net = sock_net(sk_listener); net = sock_net(sk_listener);
max_syn_ack_retries = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_synack_retries; max_syn_ack_retries = icsk->icsk_syn_retries ? :
READ_ONCE(net->ipv4.sysctl_tcp_synack_retries);
/* Normally all the openreqs are young and become mature /* Normally all the openreqs are young and become mature
* (i.e. converted to established socket) for first timeout. * (i.e. converted to established socket) for first timeout.
* If synack was not acknowledged for 1 second, it means * If synack was not acknowledged for 1 second, it means

3
net/ipv4/tcp.c
View File

@ -3967,7 +3967,8 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
val = keepalive_probes(tp); val = keepalive_probes(tp);
break; break;
case TCP_SYNCNT: case TCP_SYNCNT:
val = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries; val = icsk->icsk_syn_retries ? :
READ_ONCE(net->ipv4.sysctl_tcp_syn_retries);
break; break;
case TCP_LINGER2: case TCP_LINGER2:
val = tp->linger2; val = tp->linger2;

10
net/ipv4/tcp_timer.c
View File

@ -239,7 +239,8 @@ static int tcp_write_timeout(struct sock *sk)
if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
if (icsk->icsk_retransmits) if (icsk->icsk_retransmits)
__dst_negative_advice(sk); __dst_negative_advice(sk);
retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries; retry_until = icsk->icsk_syn_retries ? :
READ_ONCE(net->ipv4.sysctl_tcp_syn_retries);
expired = icsk->icsk_retransmits >= retry_until; expired = icsk->icsk_retransmits >= retry_until;
} else { } else {
if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) { if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) {
@ -406,12 +407,15 @@ abort: tcp_write_err(sk);
static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req)
{ {
struct inet_connection_sock *icsk = inet_csk(sk); struct inet_connection_sock *icsk = inet_csk(sk);
int max_retries = icsk->icsk_syn_retries ? :
sock_net(sk)->ipv4.sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
struct tcp_sock *tp = tcp_sk(sk); struct tcp_sock *tp = tcp_sk(sk);
int max_retries;
req->rsk_ops->syn_ack_timeout(req); req->rsk_ops->syn_ack_timeout(req);
/* add one more retry for fastopen */
max_retries = icsk->icsk_syn_retries ? :
READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1;
if (req->num_timeout >= max_retries) { if (req->num_timeout >= max_retries) {
tcp_write_err(sk); tcp_write_err(sk);
return; return;