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Commit 38661fe6 authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
Browse files

tcp_metrics: annotate data-races around tm->tcpm_stamp 



[ 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: 51c5d0c4 ("tcp: Maintain dynamic metrics in local cache.")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230802131500.1478140-3-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 96f14d68

net/ipv4/tcp_metrics.c

+13 −6
Original line number Diff line number Diff line
@@ -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;
@@ -431,7 +438,7 @@ void tcp_update_metrics(struct sock *sk) 
					       tp->reordering);

		}

	}

	tm->tcpm_stamp = jiffies;

	WRITE_ONCE(tm->tcpm_stamp, jiffies);

out_unlock:

	rcu_read_unlock();

}
@@ -642,7 +649,7 @@ 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;