[PATCH 6.1 068/127] tcp_metrics: annotate data-races around tm->tcpm_net

Greg Kroah-Hartman
2023-08-09T10:55:10Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit d5d986ce42c71a7562d32c4e21e026b0f87befec ]

tm->tcpm_net can be read or written locklessly.

Instead of changing write_pnet() and read_pnet() and potentially
hurt performance, add the needed READ_ONCE()/WRITE_ONCE()
in tm_net() and tcpm_new().

Fixes: 849e8a0ca8d5 ("tcp_metrics: Add a field tcpm_net and verify it matches on lookup")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230802131500.1478140-6-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/tcp_metrics.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index fd4ab7a51cef2..4fd274836a48f 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -40,7 +40,7 @@ struct tcp_fastopen_metrics {

struct tcp_metrics_block {
struct tcp_metrics_block __rcu *tcpm_next;
- possible_net_t tcpm_net;
+ struct net *tcpm_net;
struct inetpeer_addr tcpm_saddr;
struct inetpeer_addr tcpm_daddr;
unsigned long tcpm_stamp;
@@ -51,9 +51,10 @@ struct tcp_metrics_block {
struct rcu_head rcu_head;
};

-static inline struct net *tm_net(struct tcp_metrics_block *tm)
+static inline struct net *tm_net(const struct tcp_metrics_block *tm)
{
- return read_pnet(&tm->tcpm_net);
+ /* Paired with the WRITE_ONCE() in tcpm_new() */
+ return READ_ONCE(tm->tcpm_net);
}

static bool tcp_metric_locked(struct tcp_metrics_block *tm,
@@ -197,7 +198,9 @@ static struct tcp_metrics_block *tcpm_new(struct dst_entry *dst,
if (!tm)
goto out_unlock;
}
- write_pnet(&tm->tcpm_net, net);
+ /* Paired with the READ_ONCE() in tm_net() */
+ WRITE_ONCE(tm->tcpm_net, net);
+
tm->tcpm_saddr = *saddr;
tm->tcpm_daddr = *daddr;

--
2.40.1