Patch "tcp: annotate data-races around tp->keepalive_time" has been added to the 6.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    tcp: annotate data-races around tp->keepalive_time

to the 6.4-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-annotate-data-races-around-tp-keepalive_time.patch
and it can be found in the queue-6.4 subdirectory.

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



commit 2eef7f4c025ee2aa146f34a5772cc1b7a238dbca
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Wed Jul 19 21:28:49 2023 +0000

    tcp: annotate data-races around tp->keepalive_time
    
    [ Upstream commit 4164245c76ff906c9086758e1c3f87082a7f5ef5 ]
    
    do_tcp_getsockopt() reads tp->keepalive_time while another cpu
    might change its value.
    
    Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230719212857.3943972-4-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 5066e4586cf09..9a12e8c09ea04 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1522,9 +1522,12 @@ static inline int keepalive_intvl_when(const struct tcp_sock *tp)
 static inline int keepalive_time_when(const struct tcp_sock *tp)
 {
 	struct net *net = sock_net((struct sock *)tp);
+	int val;
 
-	return tp->keepalive_time ? :
-		READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
+	/* Paired with WRITE_ONCE() in tcp_sock_set_keepidle_locked() */
+	val = READ_ONCE(tp->keepalive_time);
+
+	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
 }
 
 static inline int keepalive_probes(const struct tcp_sock *tp)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 15b1191411ec3..c3b743093d482 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3421,7 +3421,8 @@ int tcp_sock_set_keepidle_locked(struct sock *sk, int val)
 	if (val < 1 || val > MAX_TCP_KEEPIDLE)
 		return -EINVAL;
 
-	tp->keepalive_time = val * HZ;
+	/* Paired with WRITE_ONCE() in keepalive_time_when() */
+	WRITE_ONCE(tp->keepalive_time, val * HZ);
 	if (sock_flag(sk, SOCK_KEEPOPEN) &&
 	    !((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))) {
 		u32 elapsed = keepalive_time_elapsed(tp);