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

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Message-ID: <CAH1kMwQ+vAcqcbsimB2Rr8gyhLtjPEQYi11uVi48Rm5PQRmpoA@mail.gmail.com>
Date:   Mon, 25 Apr 2022 23:17:25 +0530
From:   Vihas Makwana <makvihas@...il.com>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Straube <straube.linux@...il.com>,
        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

On Mon, Apr 25, 2022 at 12:23 AM Pavel Skripkin <paskripkin@...il.com> wrote:
>
> 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).
>
Oh, I see.
> >
> >       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



-- 
Thanks,
Vihas