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

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Message-ID: <YMjuPtKtiaVLLO0q@google.com>
Date:   Tue, 15 Jun 2021 11:15:26 -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()

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