[PATCH 4.19 19/62] tcp: Fix data-races around sysctl_tcp_reordering.

Greg Kroah-Hartman
2022-07-27T16:35:28Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 46778cd16e6a5ad1b2e3a91f6c057c907379418e ]

While reading sysctl_tcp_reordering, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its 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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/tcp.c | 2 +-
net/ipv4/tcp_input.c | 10 +++++++---
net/ipv4/tcp_metrics.c | 3 ++-
3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index f7795488b0ad..b1b121d5076c 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -436,7 +436,7 @@ void tcp_init_sock(struct sock *sk)
tp->snd_cwnd_clamp = ~0;
tp->mss_cache = TCP_MSS_DEFAULT;

- tp->reordering = sock_net(sk)->ipv4.sysctl_tcp_reordering;
+ tp->reordering = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reordering);
tcp_assign_congestion_control(sk);

tp->tsoffset = 0;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 92f5068c7680..afe195e03a95 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1982,6 +1982,7 @@ void tcp_enter_loss(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);
struct net *net = sock_net(sk);
bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery;
+ u8 reordering;

tcp_timeout_mark_lost(sk);

@@ -2002,10 +2003,12 @@ void tcp_enter_loss(struct sock *sk)
/* Timeout in disordered state after receiving substantial DUPACKs
* suggests that the degree of reordering is over-estimated.
*/
+ reordering = READ_ONCE(net->ipv4.sysctl_tcp_reordering);
if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
- tp->sacked_out >= net->ipv4.sysctl_tcp_reordering)
+ tp->sacked_out >= reordering)
tp->reordering = min_t(unsigned int, tp->reordering,
- net->ipv4.sysctl_tcp_reordering);
+ reordering);
+
tcp_set_ca_state(sk, TCP_CA_Loss);
tp->high_seq = tp->snd_nxt;
tcp_ecn_queue_cwr(tp);
@@ -3303,7 +3306,8 @@ static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
* new SACK or ECE mark may first advance cwnd here and later reduce
* cwnd in tcp_fastretrans_alert() based on more states.
*/
- if (tcp_sk(sk)->reordering > sock_net(sk)->ipv4.sysctl_tcp_reordering)
+ if (tcp_sk(sk)->reordering >
+ READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reordering))
return flag & FLAG_FORWARD_PROGRESS;

return flag & FLAG_DATA_ACKED;
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 03b51cdcc731..61843c6d7a47 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -425,7 +425,8 @@ void tcp_update_metrics(struct sock *sk)
if (!tcp_metric_locked(tm, TCP_METRIC_REORDERING)) {
val = tcp_metric_get(tm, TCP_METRIC_REORDERING);
if (val < tp->reordering &&
- tp->reordering != net->ipv4.sysctl_tcp_reordering)
+ tp->reordering !=
+ READ_ONCE(net->ipv4.sysctl_tcp_reordering))
tcp_metric_set(tm, TCP_METRIC_REORDERING,
tp->reordering);
}
--
2.35.1