Patch "tcp: annotate data-races around tp->keepalive_intvl" 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_intvl

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_intvl.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 eb1f807c757603fcae643c60d5656a557d7fcf23
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Wed Jul 19 21:28:50 2023 +0000

    tcp: annotate data-races around tp->keepalive_intvl
    
    [ Upstream commit 5ecf9d4f52ff2f1d4d44c9b68bc75688e82f13b4 ]
    
    do_tcp_getsockopt() reads tp->keepalive_intvl 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/20230719212857.3943972-5-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 9a12e8c09ea04..45d50a40795da 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1514,9 +1514,14 @@ void tcp_leave_memory_pressure(struct sock *sk);
 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
 {
 	struct net *net = sock_net((struct sock *)tp);
+	int val;
+
+	/* Paired with WRITE_ONCE() in tcp_sock_set_keepintvl()
+	 * and do_tcp_setsockopt().
+	 */
+	val = READ_ONCE(tp->keepalive_intvl);
 
-	return tp->keepalive_intvl ? :
-		READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
+	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
 }
 
 static inline int keepalive_time_when(const struct tcp_sock *tp)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c3b743093d482..514817119bd4d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3454,7 +3454,7 @@ int tcp_sock_set_keepintvl(struct sock *sk, int val)
 		return -EINVAL;
 
 	lock_sock(sk);
-	tcp_sk(sk)->keepalive_intvl = val * HZ;
+	WRITE_ONCE(tcp_sk(sk)->keepalive_intvl, val * HZ);
 	release_sock(sk);
 	return 0;
 }
@@ -3668,7 +3668,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 		if (val < 1 || val > MAX_TCP_KEEPINTVL)
 			err = -EINVAL;
 		else
-			tp->keepalive_intvl = val * HZ;
+			WRITE_ONCE(tp->keepalive_intvl, val * HZ);
 		break;
 	case TCP_KEEPCNT:
 		if (val < 1 || val > MAX_TCP_KEEPCNT)