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 <YMjuPtKtiaVLLO0q@google.com>
In-Reply-To: <YMjuPtKtiaVLLO0q@google.com>
From:   Yizhuo Zhai <yzhai003@ucr.edu>
Date:   Tue, 15 Jun 2021 11:57:36 -0700
Message-ID: <CABvMjLSKe2ojoVTZOwv_Dr4P4rsDa334vBc_-T8sMTPUJ-f==g@mail.gmail.com>
Subject: Re: [PATCH] Input: hideep - fix the uninitialized use in hideep_nvm_unlock()
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Demitry:

Thanks for your quick response, following your advice, a careful way
is changing the return type of  "hideep_nvm_unlock()" from void to
int, and its caller "hideep_program_nvm()" also needs to add the
return check.

If this sounds ok, I would go ahead to modify the patch accordingly.

On Tue, Jun 15, 2021 at 11:15 AM Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
>
> Hi Yizhuo,
>
> On Tue, Jun 15, 2021 at 10:26:09AM -0700, Yizhuo Zhai wrote:
> > Inside function hideep_nvm_unlock(), variable "unmask_code" could
> > be uninitialized if hideep_pgm_r_reg() returns error, however, it
> > is used in the later if statement after an "and" operation, which
> > is potentially unsafe.
>
> I do not think that simply initializing the variable makes the code
> behave any better. If we want to fix this properly we need to check for
> errors returned by hideep_pgm_r_reg() and hideep_pgm_w_reg() and exit
> this function early, signalling the caller about errors.
>
> >
> > Signed-off-by: Yizhuo <yzhai003@ucr.edu>
> > ---
> >  drivers/input/touchscreen/hideep.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/input/touchscreen/hideep.c
> > b/drivers/input/touchscreen/hideep.c
> > index ddad4a82a5e5..49b713ad4384 100644
> > --- a/drivers/input/touchscreen/hideep.c
> > +++ b/drivers/input/touchscreen/hideep.c
> > @@ -363,7 +363,7 @@ static int hideep_enter_pgm(struct hideep_ts *ts)
> >
> >  static void hideep_nvm_unlock(struct hideep_ts *ts)
> >  {
> > -       u32 unmask_code;
> > +       u32 unmask_code = 0;
> >
> >         hideep_pgm_w_reg(ts, HIDEEP_FLASH_CFG, HIDEEP_NVM_SFR_RPAGE);
> >         hideep_pgm_r_reg(ts, 0x0000000C, &unmask_code);
> > --
> > 2.17.1
>
> Thanks.
>
> --
> Dmitry


-- 
Kind Regards,

Yizhuo Zhai

Computer Science, Graduate Student
University of California, Riverside