Subject: Re: [PATCH v3 net] af_unix: Update unix_sk(sk)->oob_skb under sk_receive_queue lock.

From: Simon Horman <[email-masked]>
Date: Mon, 13 May 2024 17:57:47 +0100

On Mon, May 13, 2024 at 10:06:28PM +0900, Kuniyuki Iwashima wrote:

...

> @@ -2666,13 +2681,19 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
>  			} else if (flags & MSG_PEEK) {
>  				skb = NULL;
>  			} else {
> -				skb_unlink(skb, &sk->sk_receive_queue);
> +				__skb_unlink(skb, &sk->sk_receive_queue);
>  				WRITE_ONCE(u->oob_skb, NULL);
> -				if (!WARN_ON_ONCE(skb_unref(skb)))
> -					kfree_skb(skb);
> +				unlinked_skb = skb;
>  				skb = skb_peek(&sk->sk_receive_queue);
>  			}
>  		}
> +
> +		spin_unlock(&sk->sk_receive_queue.lock);
> +
> +		if (unlinked_skb) {
> +			WARN_ON_ONCE(skb_unref(skb));
> +			kfree_skb(skb);

Hi Iwashima-san,

Here skb is kfree'd.

> +		}
>  	}
>  	return skb;

But here it is returned.
This doesn't seem right.

Flagged by Smatch.

>  }

...

-- 
pw-bot: changes-requested