linux-kernel - Re: [PATCH] soc: mediatek: pwrap: Zero initialize rdata in pwrap_init

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Message-ID: <20190320191118.GE28744@archlinux-ryzen>
Date:   Wed, 20 Mar 2019 12:11:18 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] soc: mediatek: pwrap: Zero initialize rdata in
 pwrap_init_cipher

On Thu, Mar 07, 2019 at 03:56:51PM -0700, Nathan Chancellor wrote:
> When building with -Wsometimes-uninitialized, Clang warns:
> 
> drivers/soc/mediatek/mtk-pmic-wrap.c:1358:6: error: variable 'rdata' is
> used uninitialized whenever '||' condition is true
> [-Werror,-Wsometimes-uninitialized]
> 
> If pwrap_write returns non-zero, pwrap_read will not be called to
> initialize rdata, meaning that we will use some random uninitialized
> stack value in our print statement. Zero initialize rdata in case this
> happens.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/401
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
> 
> I don't know if this is better or to just restructure the if statement
> below (I'm not an expert in this code so I'll leave that up to the
> maintainers to decide).
> 
>  drivers/soc/mediatek/mtk-pmic-wrap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/mediatek/mtk-pmic-wrap.c b/drivers/soc/mediatek/mtk-pmic-wrap.c
> index 8236a6c87e19..2f632e8790f7 100644
> --- a/drivers/soc/mediatek/mtk-pmic-wrap.c
> +++ b/drivers/soc/mediatek/mtk-pmic-wrap.c
> @@ -1281,7 +1281,7 @@ static bool pwrap_is_pmic_cipher_ready(struct pmic_wrapper *wrp)
>  static int pwrap_init_cipher(struct pmic_wrapper *wrp)
>  {
>  	int ret;
> -	u32 rdata;
> +	u32 rdata = 0;
>  
>  	pwrap_writel(wrp, 0x1, PWRAP_CIPHER_SWRST);
>  	pwrap_writel(wrp, 0x0, PWRAP_CIPHER_SWRST);
> -- 
> 2.21.0
> 

Gentle ping (if there was a response to this, I didn't receive it). I
know I sent it in the middle of a merge window so I get if it slipped
through the cracks.

Thanks,
Nathan