linux-kernel - Re: [PATCH Linux-next] ioctl_linux: fix a potential NULL pointer dereference bug

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Date:   Mon, 23 Aug 2021 22:34:54 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     cgel.zte@...il.com, gregkh@...uxfoundation.org
Cc:     linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        xu xin <xu.xin16@....com.cn>, Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH Linux-next] ioctl_linux: fix a potential NULL pointer
 dereference bug

On 8/23/21 6:06 AM, cgel.zte@...il.com wrote:
> From: xu xin <xu.xin16@....com.cn>
> 
> The pointer might be NULL, but it is dereferenced.
> 
> Reported-by: Zeal Robot <zealci@....com.cn>
> Signed-off-by: xu xin <xu.xin16@....com.cn>
> ---
>   drivers/staging/r8188eu/os_dep/ioctl_linux.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/r8188eu/os_dep/ioctl_linux.c b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> index a3e6d761e748..ce4ce9190f5f 100644
> --- a/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> +++ b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
> @@ -4389,7 +4389,8 @@ static int rtw_dbg_port(struct net_device *dev,
>   				pregpriv->rx_stbc = extra_arg;
>   				DBG_88E("set rx_stbc =%d\n", pregpriv->rx_stbc);
>   			} else {
> -				DBG_88E("get rx_stbc =%d\n", pregpriv->rx_stbc);
> +				if (pregpriv)
> +					DBG_88E("get rx_stbc =%d\n", pregpriv->rx_stbc);
>   			}
>   		}
>   			break;
> @@ -4401,7 +4402,8 @@ static int rtw_dbg_port(struct net_device *dev,
>   				pregpriv->ampdu_enable = extra_arg;
>   				DBG_88E("set ampdu_enable =%d\n", pregpriv->ampdu_enable);
>   			} else {
> -				DBG_88E("get ampdu_enable =%d\n", pregpriv->ampdu_enable);
> +				if (pregpriv)
> +					DBG_88E("get ampdu_enable =%d\n", pregpriv->ampdu_enable);
>   			}
>   		}
>   			break;
> 


Hi, Xu!

I can't see how pregpriv can be NULL:

	struct registry_priv *pregpriv = &padapter->registrypriv;

It can be NULL in case of completely wrong padapter pointer, but I can't 
see how it's possible. Do you have a calltrace?

I guess, your robot reported this, because there is useless check in 
same code block:

	if (pregpriv &&
		(extra_arg == 0 ||
		 extra_arg == 1 ||
		 extra_arg == 2 ||
		 extra_arg == 3))


So, I think, "pregpriv &&" part should be removed, instead of adding 2 
branches.


Also, subject line should be "staging: r8118eu: <subject>". Thank you!



With regards,
Pavel Skripkin