linux-kernel - Re: [PATCH] Input: hideep - fix the uninitialized use in hideep_nvm

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Message-ID: <YMkCfykNyHtuMUkY@google.com>
Date:   Tue, 15 Jun 2021 12:41:51 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Yizhuo Zhai <yzhai003@....edu>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: hideep - fix the uninitialized use in
 hideep_nvm_unlock()

On Tue, Jun 15, 2021 at 11:57:36AM -0700, Yizhuo Zhai wrote:
> 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.

Yes, this sounds right.

> 
> On Tue, Jun 15, 2021 at 11:15 AM Dmitry Torokhov
> <dmitry.torokhov@...il.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@....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

-- 
Dmitry