[PATCH 6.1 065/127] tcp_metrics: annotate data-races around tm->tcpm_stamp

Greg Kroah-Hartman
2023-08-09T10:54:18Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 949ad62a5d5311d36fce2e14fe5fed3f936da51c ]

tm->tcpm_stamp can be read or written locklessly.

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

Also constify tcpm_check_stamp() dst argument.

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/20230802131500.1478140-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/tcp_metrics.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index c4daf0aa2d4d9..8386165887963 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -97,7 +97,7 @@ static void tcpm_suck_dst(struct tcp_metrics_block *tm,
u32 msval;
u32 val;

- tm->tcpm_stamp = jiffies;
+ WRITE_ONCE(tm->tcpm_stamp, jiffies);

val = 0;
if (dst_metric_locked(dst, RTAX_RTT))
@@ -131,9 +131,15 @@ static void tcpm_suck_dst(struct tcp_metrics_block *tm,

#define TCP_METRICS_TIMEOUT (60 * 60 * HZ)

-static void tcpm_check_stamp(struct tcp_metrics_block *tm, struct dst_entry *dst)
+static void tcpm_check_stamp(struct tcp_metrics_block *tm,
+ const struct dst_entry *dst)
{
- if (tm && unlikely(time_after(jiffies, tm->tcpm_stamp + TCP_METRICS_TIMEOUT)))
+ unsigned long limit;
+
+ if (!tm)
+ return;
+ limit = READ_ONCE(tm->tcpm_stamp) + TCP_METRICS_TIMEOUT;
+ if (unlikely(time_after(jiffies, limit)))
tcpm_suck_dst(tm, dst, false);
}

@@ -174,7 +180,8 @@ static struct tcp_metrics_block *tcpm_new(struct dst_entry *dst,
oldest = deref_locked(tcp_metrics_hash[hash].chain);
for (tm = deref_locked(oldest->tcpm_next); tm;
tm = deref_locked(tm->tcpm_next)) {
- if (time_before(tm->tcpm_stamp, oldest->tcpm_stamp))
+ if (time_before(READ_ONCE(tm->tcpm_stamp),
+ READ_ONCE(oldest->tcpm_stamp)))
oldest = tm;
}
tm = oldest;
@@ -434,7 +441,7 @@ void tcp_update_metrics(struct sock *sk)
tp->reordering);
}
}
- tm->tcpm_stamp = jiffies;
+ WRITE_ONCE(tm->tcpm_stamp, jiffies);
out_unlock:
rcu_read_unlock();
}
@@ -647,7 +654,7 @@ static int tcp_metrics_fill_info(struct sk_buff *msg,
}

if (nla_put_msecs(msg, TCP_METRICS_ATTR_AGE,
- jiffies - tm->tcpm_stamp,
+ jiffies - READ_ONCE(tm->tcpm_stamp),
TCP_METRICS_ATTR_PAD) < 0)
goto nla_put_failure;

--
2.40.1