linux-kernel - RE: [PATCH v6] kernel.h: Retain constant expression output for max()/min()

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Message-ID: <0c29e85f7fa64ff488d60b0f5647257b@AcuMS.aculab.com>
Date:   Tue, 27 Mar 2018 08:55:55 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Kees Cook' <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Martin Uecker <Martin.Uecker@....uni-goettingen.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Randy Dunlap <rdunlap@...radead.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        "Ingo Molnar" <mingo@...nel.org>, Ian Abbott <abbotti@....co.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>
Subject: RE: [PATCH v6] kernel.h: Retain constant expression output for
 max()/min()

From: Kees Cook
> Sent: 26 March 2018 23:16
...
> +#define __typecheck(x, y) \
> +		(!!(sizeof((typeof(x)*)1 == (typeof(y)*)1)))

The two 1 should probably be at least 8 before the compiler starts
bleating about accesses to misaligned addresses being undefined.

	David