[PATCH 5.18 119/158] tcp: Fix data-races around sysctl_tcp_recovery.

Greg Kroah-Hartman
2022-07-27T17:42:15Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit e7d2ef837e14a971a05f60ea08c47f3fed1a36e4 ]

While reading sysctl_tcp_recovery, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

Fixes: 4f41b1c58a32 ("tcp: use RACK to detect losses")
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_input.c | 3 ++-
net/ipv4/tcp_recovery.c | 6 ++++--
2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c2431fe41b09..61f93f51adbb 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2095,7 +2095,8 @@ static inline void tcp_init_undo(struct tcp_sock *tp)

static bool tcp_is_rack(const struct sock *sk)
{
- return sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION;
+ return READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
+ TCP_RACK_LOSS_DETECTION;
}

/* If we detect SACK reneging, forget all SACK information
diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
index fd113f6226ef..ac14216f6204 100644
--- a/net/ipv4/tcp_recovery.c
+++ b/net/ipv4/tcp_recovery.c
@@ -19,7 +19,8 @@ static u32 tcp_rack_reo_wnd(const struct sock *sk)
return 0;

if (tp->sacked_out >= tp->reordering &&
- !(sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_NO_DUPTHRESH))
+ !(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
+ TCP_RACK_NO_DUPTHRESH))
return 0;
}

@@ -192,7 +193,8 @@ void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs)
{
struct tcp_sock *tp = tcp_sk(sk);

- if (sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_STATIC_REO_WND ||
+ if ((READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
+ TCP_RACK_STATIC_REO_WND) ||
!rs->prior_delivered)
return;

--
2.35.1