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

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Message-ID: <CA+55aFyiCg23eL=y0nE8a-6_tBAtB097J8v_BtpUcHU8sc3hyQ@mail.gmail.com>
Date:	Wed, 26 Nov 2014 10:58:43 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Sasha Levin <sasha.levin@...cle.com>,
	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC 1/2] compiler: use compiler to detect integer overflows

On Wed, Nov 26, 2014 at 10:50 AM, Sasha Levin <sasha.levin@...cle.com> wrote:
>
> The kernel still has it's share of *signed* integer overflows. Example? fadvise64_64():

Yes, those would definitely be worth fixing.

[ Although quite frankly, since I know gcc already knows about the
whole "check for overflow" pattern, from a QoI standpoint it is sad
that it then might optimize it away. Kind of like how it would trust
the type-based strict alias analysis more than the obvious *static*
alias analysis. Oh well ]

I don't think coccinelle can do signedness checks, though, especially
of the kind that are hidden deep behind some typedef like "loff_t".
Maybe I'm wrong. Maybe smatch can? Adding Dan Carpenter to the cc..

                             Linus
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