From: Jason Xing <kernelxing@tencent.com>

It's possible that writer and the reader can manipulate the same
sysctl knob concurrently. Using READ_ONCE() to prevent reading
an old value.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 net/mptcp/protocol.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index f16edef6026a..a10ebf3ee10a 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -850,7 +850,7 @@ static inline void __mptcp_sync_sndbuf(struct sock *sk)
 	if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
 		return;
 
-	new_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[0];
+	new_sndbuf = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[0]);
 	mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
 		ssk_sndbuf =  READ_ONCE(mptcp_subflow_tcp_sock(subflow)->sk_sndbuf);
 
-- 
2.37.3

On Fri, 8 Mar 2024, Jason Xing wrote:

> From: Jason Xing <kernelxing@tencent.com>
>
> It's possible that writer and the reader can manipulate the same
> sysctl knob concurrently. Using READ_ONCE() to prevent reading
> an old value.
>
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> ---
> net/mptcp/protocol.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
> index f16edef6026a..a10ebf3ee10a 100644
> --- a/net/mptcp/protocol.h
> +++ b/net/mptcp/protocol.h
> @@ -850,7 +850,7 @@ static inline void __mptcp_sync_sndbuf(struct sock *sk)
> 	if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
> 		return;
>
> -	new_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[0];
> +	new_sndbuf = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[0]);
> 	mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
> 		ssk_sndbuf =  READ_ONCE(mptcp_subflow_tcp_sock(subflow)->sk_sndbuf);
>

Looks good to me, thanks Jason.

Reviewed-by: Mat Martineau <martineau@kernel.org>

On Fri, Mar 8, 2024 at 12:25 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> From: Jason Xing <kernelxing@tencent.com>
>
> It's possible that writer and the reader can manipulate the same
> sysctl knob concurrently. Using READ_ONCE() to prevent reading
> an old value.
>
> Signed-off-by: Jason Xing <kernelxing@tencent.com>

Reviewed-by: Eric Dumazet <edumazet@google.com>