Patch "tcp_metrics: annotate data-races around tm->tcpm_net" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    tcp_metrics: annotate data-races around tm->tcpm_net

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp_metrics-annotate-data-races-around-tm-tcpm_net.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 5440121210f955781f75e5cfd95ac199f70c1b99
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Wed Aug 2 13:14:59 2023 +0000

    tcp_metrics: annotate data-races around tm->tcpm_net
    
    [ 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@xxxxxxxxxx>
    Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
    Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230802131500.1478140-6-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 0c309fd4e04b2..88b0d952a2888 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;