From: Linus Torvalds <torvalds@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Florian Weimer <fweimer@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Randy Dunlap <rdunlap@infradead.org>,
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
David Laight <David.Laight@aculab.com>,
Ian Abbott <abbotti@mev.co.uk>,
linux-input <linux-input@vger.kernel.org>,
linux-btrfs <linux-btrfs@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH v5 0/2] Remove false-positive VLAs when using max()
Date: Tue, 20 Mar 2018 16:26:52 -0700 [thread overview]
Message-ID: <CA+55aFwO8KZD_tZwqwL05FbzpKW4Ucd88C0tcR7LJ1utuy3WGg@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFwxk=tUECYQkd4cog08qW4ZT=r2K7FQXzGnc-zuMc7JQA@mail.gmail.com>
On Tue, Mar 20, 2018 at 4:23 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Hmm. So thanks to the diseased mind of Martin Uecker, there's a better
> test for "__is_constant()":
>
> /* Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> */
> #define __is_constant(a) \
> (sizeof(int) == sizeof(*(1 ? ((void*)((a) * 0l)) : (int*)1)))
>
> that is actually *specified* by the C standard to work, and doesn't
> even depend on any gcc extensions.
Well, it does depend on 'sizeof(*(void *)X)' being 1 and the compiler
not complaining about it, and that sizeof(int) is not 1.
But since we depend on those things in the kernel anyway, that's fine.
Linus
next prev parent reply other threads:[~2018-03-20 23:26 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-16 4:25 [PATCH v5 0/2] Remove false-positive VLAs when using max() Kees Cook
2018-03-16 4:25 ` [PATCH v5 1/2] kernel.h: Introduce const_max_t() for VLA removal Kees Cook
2018-03-16 4:25 ` [PATCH v5 2/2] Remove false-positive VLAs when using max() Kees Cook
2018-03-19 10:45 ` Andrey Ryabinin
2018-03-16 11:47 ` [PATCH v5 0/2] " Florian Weimer
2018-03-16 17:29 ` Linus Torvalds
2018-03-16 17:32 ` Florian Weimer
2018-03-16 17:44 ` David Laight
2018-03-16 20:25 ` Linus Torvalds
2018-03-16 17:55 ` Al Viro
2018-03-16 18:14 ` Al Viro
2018-03-16 19:27 ` Linus Torvalds
2018-03-16 20:03 ` Miguel Ojeda
2018-03-16 20:14 ` Linus Torvalds
2018-03-16 20:19 ` Linus Torvalds
2018-03-17 0:48 ` Miguel Ojeda
2018-03-17 1:49 ` Miguel Ojeda
2018-03-16 20:12 ` Al Viro
2018-03-16 20:15 ` Linus Torvalds
2018-03-16 20:18 ` Al Viro
2018-03-17 7:27 ` Kees Cook
2018-03-17 18:52 ` Linus Torvalds
2018-03-17 20:07 ` Kees Cook
2018-03-17 22:55 ` Josh Poimboeuf
2018-03-20 23:23 ` Linus Torvalds
2018-03-20 23:26 ` Linus Torvalds [this message]
2018-03-21 0:05 ` Al Viro
2018-03-22 15:01 ` Kees Cook
2018-03-22 15:13 ` David Laight
2018-03-22 17:04 ` Linus Torvalds
2018-03-18 21:13 ` Rasmus Villemoes
2018-03-18 21:33 ` Linus Torvalds
2018-03-18 22:59 ` Rasmus Villemoes
2018-03-18 23:36 ` Linus Torvalds
2018-03-19 9:43 ` David Laight
2018-03-19 23:29 ` Linus Torvalds
2018-03-20 3:10 ` Arnd Bergmann
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