linux-kernel - Re: [PATCH] um: vector: fix return value check in vector_legacy

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Message-ID: <CAFLxGvytpwjXM0bdLrxt0itfEBPqJSmuM6otB7dTBmsTaAAPgw@mail.gmail.com>
Date: Thu, 4 Jan 2024 22:05:50 +0100
From: Richard Weinberger <richard.weinberger@...il.com>
To: Ma Ke <make_ruc2021@....com>
Cc: richard@....at, anton.ivanov@...bridgegreys.com, johannes@...solutions.net, 
	xiangyang3@...wei.com, linux-um@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] um: vector: fix return value check in vector_legacy_rx

On Fri, Oct 6, 2023 at 2:28 PM Ma Ke <make_ruc2021@....com> wrote:
>
> In vector_legacy_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@....com>
> ---
>  arch/um/drivers/vector_kern.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/um/drivers/vector_kern.c b/arch/um/drivers/vector_kern.c
> index 131b7cb29576..822a8c0cdcc1 100644
> --- a/arch/um/drivers/vector_kern.c
> +++ b/arch/um/drivers/vector_kern.c
> @@ -890,7 +890,8 @@ static int vector_legacy_rx(struct vector_private *vp)
>                                         skb->ip_summed = CHECKSUM_UNNECESSARY;
>                                 }
>                         }
> -                       pskb_trim(skb, pkt_len - vp->rx_header_size);
> +                       if (pskb_trim(skb, pkt_len - vp->rx_header_size))
> +                               return 0;

I think this adds a memory leak. Also, can pskb_trim() really fail in
this scenario?
The function controls skb creation and knows all lengths.