[PATCH] net: mark racy access on sk->sk_rcvbuf

[PATCH] net: mark racy access on sk->sk_rcvbuf

[linke li]

sk->sk_rcvbuf can be changed by other threads. Mark this as benign using
READ_ONCE. 

This patch is aimed at reducing the number of benign races reported by
KCSAN in order to focus future debugging effort on harmful races.

Signed-off-by: linke li <lilinke99@qq.com>
---
 net/core/sock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 5e78798456fd..4c5524e70534 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -551,7 +551,7 @@ int __sk_receive_skb(struct sock *sk, struct sk_buff *skb,
 
 	skb->dev = NULL;
 
-	if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {
+	if (sk_rcvqueues_full(sk, READ_ONCE(sk->sk_rcvbuf))) {
 		atomic_inc(&sk->sk_drops);
 		goto discard_and_relse;
 	}
-- 
2.39.3 (Apple Git-146)

Re: [PATCH] net: mark racy access on sk->sk_rcvbuf

[Eric Dumazet]

On Sat, Mar 9, 2024 at 2:35 PM linke li <lilinke99@qq.com> wrote:
>
> sk->sk_rcvbuf can be changed by other threads. Mark this as benign using
> READ_ONCE.
>
> This patch is aimed at reducing the number of benign races reported by
> KCSAN in order to focus future debugging effort on harmful races.
>
> Signed-off-by: linke li <lilinke99@qq.com>
> ---
>  net/core/sock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 5e78798456fd..4c5524e70534 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -551,7 +551,7 @@ int __sk_receive_skb(struct sock *sk, struct sk_buff *skb,
>
>         skb->dev = NULL;
>
> -       if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {
> +       if (sk_rcvqueues_full(sk, READ_ONCE(sk->sk_rcvbuf))) {
>                 atomic_inc(&sk->sk_drops);
>                 goto discard_and_relse;

OK, but what about __sock_queue_rcv_skb() in the same file ?

Re: [PATCH] net: mark racy access on sk->sk_rcvbuf

[linke li]

> OK, but what about __sock_queue_rcv_skb() in the same file ?

I notice that, but I am not very sure whether there is a data race. If it
is a similar situation, then the same patch should be applied too.

Re: [PATCH] net: mark racy access on sk->sk_rcvbuf

[Jason Xing]

On Sat, Mar 9, 2024 at 10:10 PM linke li <lilinke99@qq.com> wrote:
>
> > OK, but what about __sock_queue_rcv_skb() in the same file ?
>
> I notice that, but I am not very sure whether there is a data race. If it
> is a similar situation, then the same patch should be applied too.

During that process, I see no lock owning the socket, so sk->sk_rcvbuf
should also be read locklessly.

Thanks,
Jason

>
>