linux-kernel - Re: [PATCH] string: Improve the generic strlcpy() implementation

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Date:	Mon, 5 Oct 2015 18:03:31 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Chris Metcalf <cmetcalf@...hip.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Borislav Petkov <bp@...en8.de>,
	open list <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] string: Improve the generic strlcpy() implementation


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> So I don't think a "generic" range check helper can force types like
> "unsigned long".

Yeah.

> That said, doing a simple
> 
>     git grep '<.*||.*>'
> 
> does show that the "positive or non-zero ranges with constant range
> limits" case is fairly common, and maybe we could have a macro that
> does some magic compile-time checking that (a) the range really is a
> compile-time constant and (b) that range is valid and (c) avoids the
> comparison with zero if the expression to be tested is unsigned.
> 
> So it is possible that we could enable type limit checking if we also
> introduce a good way to not then create crap patches that actually
> make the code more fragile or less readable. I'm not violently against
> that. But I *am* violently against introducing that braindead warning
> without very clear rules that we don't then have the mindless and
> wrong changes to remove proper and obvious range checking and replace
> it with "the expression is unsigned so we remove the nice readable
> lower bounds check as unnecessary".

Ok, and fully agreed.

Thanks,

	Ingo
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