linux-hardening - Re: [PATCH v4 2/3] drivers/soc/renesas: Prefer memcpy over strcpy

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Date:   Sun, 8 Aug 2021 17:35:54 +0200
From:   Bernd Petrovitsch <bernd@...rovitsch.priv.at>
To:     Len Baker <len.baker@....com>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Santosh Shilimkar <ssantosh@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        David Laight <David.Laight@...LAB.COM>,
        Robin Murphy <robin.murphy@....com>,
        linux-hardening@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 2/3] drivers/soc/renesas: Prefer memcpy over strcpy

Hi all!

On 08/08/2021 14:50, Len Baker wrote:
> strcpy() performs no bounds checking on the destination buffer. This
> could result in linear overflows beyond the end of the buffer, leading
> to all kinds of misbehaviors. So, use memcpy() as a safe replacement.
> 
> This is a previous step in the path to remove the strcpy() function
> entirely from the kernel.
> 
> Signed-off-by: Len Baker <len.baker@....com>
> ---
>  drivers/soc/renesas/r8a779a0-sysc.c | 6 ++++--
>  drivers/soc/renesas/rcar-sysc.c     | 6 ++++--
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/soc/renesas/r8a779a0-sysc.c b/drivers/soc/renesas/r8a779a0-sysc.c
> index d464ffa1be33..7410b9fa9846 100644
> --- a/drivers/soc/renesas/r8a779a0-sysc.c
> +++ b/drivers/soc/renesas/r8a779a0-sysc.c
> @@ -404,19 +404,21 @@ static int __init r8a779a0_sysc_pd_init(void)
>  	for (i = 0; i < info->num_areas; i++) {
>  		const struct r8a779a0_sysc_area *area = &info->areas[i];
>  		struct r8a779a0_sysc_pd *pd;
> +		size_t n;
> 
>  		if (!area->name) {
>  			/* Skip NULLified area */
>  			continue;
>  		}
> 
> -		pd = kzalloc(sizeof(*pd) + strlen(area->name) + 1, GFP_KERNEL)> +		n = strlen(area->name) + 1;
> +		pd = kzalloc(sizeof(*pd) + n, GFP_KERNEL);
Zeroing the allocated bytes is not needed since it's completly
overwritten with the strcpy()/memcpy().
>  		if (!pd) {
>  			error = -ENOMEM;
>  			goto out_put;
>  		}
> 
> -		strcpy(pd->name, area->name);
> +		memcpy(pd->name, area->name, n);
>  		pd->genpd.name = pd->name;
>  		pd->pdr = area->pdr;
>  		pd->flags = area->flags;

And similar for the second hunk.

MfG,
	Bernd
-- 
Bernd Petrovitsch                  Email : bernd@...rovitsch.priv.at
     There is NO CLOUD, just other people's computers. - FSFE
                     LUGA : http://www.luga.at