RE: [PATCH bpf] skmsg: schedule psock work if the cached skb exists on the psock

[John Fastabend <john.fastabend@gmail.com>]

Liu Jian wrote:
> In sk_psock_backlog function, for ingress direction skb, if no new data
> packet arrives after the skb is cached, the cached skb does not have a
> chance to be added to the receive queue of psock. As a result, the cached
> skb cannot be received by the upper-layer application.
> 
> Fix this by reschedule the psock work to dispose the cached skb in
> sk_msg_recvmsg function.
> 
> Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
> Signed-off-by: Liu Jian <liujian56@huawei.com>
> ---

Yep thanks. We have another fix coming for a similar case with ENOMEM
through backlog. I'll post here before end of week.

Acked-by: John Fastabend <john.fastabend@gmail.com>

>  net/core/skmsg.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/net/core/skmsg.c b/net/core/skmsg.c
> index 188f8558d27d..ca70525621c7 100644
> --- a/net/core/skmsg.c
> +++ b/net/core/skmsg.c
> @@ -434,8 +434,10 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
>  			if (copied + copy > len)
>  				copy = len - copied;
>  			copy = copy_page_to_iter(page, sge->offset, copy, iter);
> -			if (!copy)
> -				return copied ? copied : -EFAULT;
> +			if (!copy) {
> +				copied = copied ? copied : -EFAULT;
> +				goto out;
> +			}
>  
>  			copied += copy;
>  			if (likely(!peek)) {
> @@ -455,7 +457,7 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
>  				 * didn't copy the entire length lets just break.
>  				 */
>  				if (copy != sge->length)
> -					return copied;
> +					goto out;
>  				sk_msg_iter_var_next(i);
>  			}
>  
> @@ -477,7 +479,9 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
>  		}
>  		msg_rx = sk_psock_peek_msg(psock);
>  	}
> -
> +out:
> +	if (psock->work_state.skb && copied > 0)
> +		schedule_work(&psock->work);
>  	return copied;
>  }
>  EXPORT_SYMBOL_GPL(sk_msg_recvmsg);
> -- 
> 2.17.1
>