linux-hardening - Re: [PATCH v3] drivers/edac/edac

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Message-ID: <YRN+8u59lJ6MWsOL@rric.localdomain>
Date:   Wed, 11 Aug 2021 09:40:34 +0200
From:   Robert Richter <rric@...nel.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Len Baker <len.baker@....com>, Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        James Morse <james.morse@....com>,
        Kees Cook <keescook@...omium.org>,
        linux-hardening@...r.kernel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] drivers/edac/edac_mc: Remove all strcpy() uses

On 10.08.21 08:02:17, Joe Perches wrote:
> On Tue, 2021-08-10 at 16:36 +0200, Robert Richter wrote:
> > On 09.08.21 10:18:58, Joe Perches wrote:
> > 
> > > strscpy and scnprintf have different return values and it's simpler
> > > and much more common to use scnprintf for appended strings that are
> > > limited to a specific buffer length.
> > 
> > Calculating the bytes written from the return value is a oneliner.
> 
> Not really.
> You still have to test for strscpy's possible return of -E2BIG.

I thought of:

	num = strscpy(p, OTHER_LABEL, len);
	num = num < 0 ? len : num;
	len -= num;
	p += num;

Clearly, this does not look nice, esp. if this is repeated in the
code. That's why I prefer the strlen(p) implementation:

	strscpy(p, OTHER_LABEL, len);
	len -= strlen(p);
	p += strlen(p);

-Robert