linux-kernel - Re: [RFC v2 1/2] compiler: use compiler to detect integer overflows

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Message-ID: <CA+55aFzTc=vXUQ8ZrWWVj4DNmrZOEr3bcYpiGt6+KEVWPW-x2g@mail.gmail.com>
Date:	Sat, 29 Nov 2014 10:08:21 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2 1/2] compiler: use compiler to detect integer overflows

On Sat, Nov 29, 2014 at 7:07 AM, Sasha Levin <sasha.levin@...cle.com> wrote:
>
> Since we can't just change those to unsigned

Sure we can. Just cast them. A signed start/len is bogus crap, it's a
random wrong type.

If you want to, add a "if (len < 0) return -EINVAL;" before the cast,
but treating negative numbers as big positive numbers sounds fine too.

> we'd still need to do an overflow
> check with signed integers somewhere.

Why? It's just a type. User space can't care, and signed values make
no sense anyway.

                 Linus
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