linux-hardening - Re: [PATCH] drivers/input: Remove all strcpy() uses in favor of strscpy()

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Date:   Sun, 1 Aug 2021 16:00:00 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Len Baker <len.baker@....com>
Cc:     Kees Cook <keescook@...omium.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, linux-hardening@...r.kernel.org,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/input: Remove all strcpy() uses in favor of
 strscpy()

On Sun, Aug 01, 2021 at 04:43:16PM +0200, 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. The safe replacement is strscpy().
> 
> Signed-off-by: Len Baker <len.baker@....com>
> ---
> This is a task of the KSPP [1]
> 
> [1] https://github.com/KSPP/linux/issues/88
> 
>  drivers/input/keyboard/locomokbd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/input/keyboard/locomokbd.c b/drivers/input/keyboard/locomokbd.c
> index dae053596572..dbb3dc48df12 100644
> --- a/drivers/input/keyboard/locomokbd.c
> +++ b/drivers/input/keyboard/locomokbd.c
> @@ -254,7 +254,7 @@ static int locomokbd_probe(struct locomo_dev *dev)
>  	locomokbd->suspend_jiffies = jiffies;
> 
>  	locomokbd->input = input_dev;
> -	strcpy(locomokbd->phys, "locomokbd/input0");
> +	strscpy(locomokbd->phys, "locomokbd/input0", sizeof(locomokbd->phys));

So if the string doesn't fit, it's fine to silently truncate it?

Rather than converting every single strcpy() in the kernel to
strscpy(), maybe there should be some consideration given to how the
issue of a strcpy() that overflows the buffer should be handled.
E.g. in the case of a known string such as the above, if it's longer
than the destination, should we find a way to make the compiler issue
a warning at compile time?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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