linux-kernel - Re: [PATCH 1/3] staging: r8188eu: fix null check in rtw_free

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Message-ID: <88d617e4-419c-0d57-b0e2-f743d208c766@gmail.com>
Date:   Sun, 24 Apr 2022 22:01:29 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Vihas Makwana <makvihas@...il.com>,
        Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Straube <straube.linux@...il.com>
Cc:     linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH 1/3] staging: r8188eu: fix null check in
 rtw_free_recvframe

Hi Vihas,

On 4/24/22 19:31, Vihas Makwana wrote:
> There's a NULL check on padapter in rtw_recv.c:170 which makes no sense as
> rtw_recv.c:152 dereferences it unconditionally and it would have already
> crashed at this point.
> Fix this by moving the dereference line inside the check.
> 
> Signed-off-by: Vihas Makwana <makvihas@...il.com>
> ---
>   drivers/staging/r8188eu/core/rtw_recv.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_recv.c b/drivers/staging/r8188eu/core/rtw_recv.c
> index c1005ddaa..4cf9b4b8f 100644
> --- a/drivers/staging/r8188eu/core/rtw_recv.c
> +++ b/drivers/staging/r8188eu/core/rtw_recv.c
> @@ -154,7 +154,6 @@ int rtw_free_recvframe(struct recv_frame *precvframe, struct __queue *pfree_recv
>   	if (!precvframe)
>   		return _FAIL;
>   	padapter = precvframe->adapter;
> -	precvpriv = &padapter->recvpriv;

This expression just an addr calculation, so it does not lead to panic 
in case of padapter being NULL

>   	if (precvframe->pkt) {
>   		dev_kfree_skb_any(precvframe->pkt);/* free skb by driver */
>   		precvframe->pkt = NULL;
> @@ -169,6 +168,7 @@ int rtw_free_recvframe(struct recv_frame *precvframe, struct __queue *pfree_recv
>   	list_add_tail(&precvframe->list, get_list_head(pfree_recv_queue));
>   
>   	if (padapter) {
> +		precvpriv = &padapter->recvpriv;
>   		if (pfree_recv_queue == &precvpriv->free_recv_queue)
>   				precvpriv->free_recvframe_cnt++;
>   	}




With regards,
Pavel Skripkin