[PATCH 6.1 066/127] tcp_metrics: annotate data-races around tm->tcpm_lock

Greg Kroah-Hartman
2023-08-09T10:56:09Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 285ce119a3c6c4502585936650143e54c8692788 ]

tm->tcpm_lock can be read or written locklessly.

Add needed READ_ONCE()/WRITE_ONCE() to document this.

Fixes: 51c5d0c4b169 ("tcp: Maintain dynamic metrics in local cache.")
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/20230802131500.1478140-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/tcp_metrics.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 8386165887963..131fa30049691 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -59,7 +59,8 @@ static inline struct net *tm_net(struct tcp_metrics_block *tm)
static bool tcp_metric_locked(struct tcp_metrics_block *tm,
enum tcp_metric_index idx)
{
- return tm->tcpm_lock & (1 << idx);
+ /* Paired with WRITE_ONCE() in tcpm_suck_dst() */
+ return READ_ONCE(tm->tcpm_lock) & (1 << idx);
}

static u32 tcp_metric_get(struct tcp_metrics_block *tm,
@@ -110,7 +111,8 @@ static void tcpm_suck_dst(struct tcp_metrics_block *tm,
val |= 1 << TCP_METRIC_CWND;
if (dst_metric_locked(dst, RTAX_REORDERING))
val |= 1 << TCP_METRIC_REORDERING;
- tm->tcpm_lock = val;
+ /* Paired with READ_ONCE() in tcp_metric_locked() */
+ WRITE_ONCE(tm->tcpm_lock, val);

msval = dst_metric_raw(dst, RTAX_RTT);
tm->tcpm_vals[TCP_METRIC_RTT] = msval * USEC_PER_MSEC;
--
2.40.1