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Date:   Sat, 7 Oct 2023 07:12:50 +0100
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Subject: Re: [PATCH] um: vector: fix return value check in vector_mmsg_rx
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To:     Ma Ke <make_ruc2021@163.com>, richard@nod.at,
        johannes@sipsolutions.net, xiangyang3@huawei.com
Cc:     linux-um@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20231007005104.3994678-1-make_ruc2021@163.com>
From:   Anton Ivanov <anton.ivanov@cambridgegreys.com>
Organization: Cambridge Greys
In-Reply-To: <20231007005104.3994678-1-make_ruc2021@163.com>
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On 07/10/2023 01:51, Ma Ke wrote:
> In vector_mmsg_rx, to avoid an unexpected result returned by
> pskb_trim, we should check the return value of pskb_trim().
> 
> Signed-off-by: Ma Ke <make_ruc2021@163.com>
> ---
>   arch/um/drivers/vector_kern.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/um/drivers/vector_kern.c b/arch/um/drivers/vector_kern.c
> index 131b7cb29576..c280ce5ea6ce 100644
> --- a/arch/um/drivers/vector_kern.c
> +++ b/arch/um/drivers/vector_kern.c
> @@ -1013,8 +1013,8 @@ static int vector_mmsg_rx(struct vector_private *vp, int budget)
>   					skb->ip_summed = CHECKSUM_UNNECESSARY;
>   				}
>   			}
> -			pskb_trim(skb,
> -				mmsg_vector->msg_len - vp->rx_header_size);
> +			if (pskb_trim(skb, mmsg_vector->msg_len - vp->rx_header_size))
> +				return 0;
>   			skb->protocol = eth_type_trans(skb, skb->dev);
>   			/*
>   			 * We do not need to lock on updating stats here

That does not look right. You can have errors when processing an 
individual packet. That is not a reason to bail and you should process 
the next ones. This way you just dropped the rest of the RX vector (up 
to 64 packets at default settings).

-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/