linux-kernel - Re: [PATCH 2/3] staging: r8188eu: fix null check in _rtw_enqueue

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Message-ID: <85f946c9-235e-cc69-4d19-1ebf972cd935@gmail.com>
Date:   Sun, 24 Apr 2022 21:53:07 +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 2/3] staging: r8188eu: fix null check in
 _rtw_enqueue_recvframe

Hi Vihas,

On 4/24/22 19:31, Vihas Makwana wrote:
> There's a NULL check on padapter in rtw_recv.c:189 which makes no sense as
> rtw_recv.c:184 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 | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_recv.c b/drivers/staging/r8188eu/core/rtw_recv.c
> index 4cf9b4b8f..7d306a3c6 100644
> --- a/drivers/staging/r8188eu/core/rtw_recv.c
> +++ b/drivers/staging/r8188eu/core/rtw_recv.c
> @@ -181,12 +181,13 @@ int rtw_free_recvframe(struct recv_frame *precvframe, struct __queue *pfree_recv
>   int _rtw_enqueue_recvframe(struct recv_frame *precvframe, struct __queue *queue)
>   {
>   	struct adapter *padapter = precvframe->adapter;
> -	struct recv_priv *precvpriv = &padapter->recvpriv;
> +	struct recv_priv *precvpriv;

Actually, `&padapter->recvpriv` is not a de-reference, it's just address 
calculation, so in case of padapder being NULL precvpriv will contain 
offsetof(struct adapter, recvpriv).

>   
>   	list_del_init(&precvframe->list);
>   	list_add_tail(&precvframe->list, get_list_head(queue));
>   
>   	if (padapter) {
> +		precvpriv = &padapter->recvpriv;
>   		if (queue == &precvpriv->free_recv_queue)
>   			precvpriv->free_recvframe_cnt++;
>   	}




With regards,
Pavel Skripkin