linux-kernel - Re: [PATCH] staging: rtl8712: Fix pointer dereferenced before checking

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Date:   Mon, 30 May 2022 10:26:40 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     baihaowen <baihaowen@...zu.com>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Florian Schilhabel <florian.c.schilhabel@...glemail.com>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8712: Fix pointer dereferenced before
 checking

On Mon, May 30, 2022 at 04:22:11PM +0800, baihaowen wrote:
> 在 2022/5/30 下午4:14, Greg Kroah-Hartman 写道:
> > On Mon, May 30, 2022 at 04:05:32PM +0800, Haowen Bai wrote:
> >> The padapter->recvpriv.signal_qual_data is dereferencing before null
> >> checking, so move it after checking.
> >>
> >> Signed-off-by: Haowen Bai <baihaowen@...zu.com>
> >> ---
> >>  drivers/staging/rtl8712/rtl8712_recv.c | 4 +++-
> >>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/staging/rtl8712/rtl8712_recv.c b/drivers/staging/rtl8712/rtl8712_recv.c
> >> index 7f1fdd058551..8ed94b259dbe 100644
> >> --- a/drivers/staging/rtl8712/rtl8712_recv.c
> >> +++ b/drivers/staging/rtl8712/rtl8712_recv.c
> >> @@ -863,10 +863,12 @@ static void process_link_qual(struct _adapter *padapter,
> >>  {
> >>  	u32	last_evm = 0, tmpVal;
> >>  	struct rx_pkt_attrib *pattrib;
> >> -	struct smooth_rssi_data *sqd = &padapter->recvpriv.signal_qual_data;
> >> +	struct smooth_rssi_data *sqd;
> >>  
> >>  	if (!prframe || !padapter)
> >>  		return;
> >> +
> >> +	sqd = &padapter->recvpriv.signal_qual_data;
> > How can padapter ever be NULL in this codepath?
> >
> > thanks,
> >
> > greg k-h
> Just the original  code, show me
> 
> if (!prframe || !padapter)
> 
> It would be null, and then return.

Again, trace things backwards, how can padapter ever be NULL?