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Message-ID: <CAGXu5jJJ4FY1BZrA6X2zKe92oJfcGBXqZr6OMx+4mXX34psrKg@mail.gmail.com>
Date: Thu, 6 Jul 2017 16:16:52 -0700
From: Kees Cook <keescook@...omium.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC/RFT PATCH] gcc-plugins: force initialize auto variables
whose addresses are taken
On Thu, Jul 6, 2017 at 2:44 PM, Kees Cook <keescook@...omium.org> wrote:
> On Thu, Jul 6, 2017 at 4:09 AM, Arnd Bergmann <arnd@...db.de> wrote:
>> On Thu, Jul 6, 2017 at 12:13 PM, Ard Biesheuvel
>> <ard.biesheuvel@...aro.org> wrote:
>>> To prevent leaking stack contents in cases where it is not possible
>>> for the compiler to figure out whether an automatic variable has been
>>> initialized or not, add a plugin that forcibly initializes all automatic
>>> variables of struct/union types if their address is taken at any point.
>>>
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>
> Ard, I'd be curious what you see for "size" difference between builds
> and if it's visible with hackbench or other things?
Hm, not all that bad on the size front:
text data bss dec
hex filename
10950705 5592525 13955072 30498302 1d15dfe vmlinux
11048035 5592365 13955072 30595472 1d2d990
vmlinux.initautobyref
And yes, as expected, wow there are a lot of notices in verbose mode. ;)
My pet favorite, from the NAKed patch I sent forever ago, is covered
(as expected):
net/socket.c: In function ‘SYSC_getsockname’:
net/socket.c:1605:26: note: auto variable will be forcibly initialized
struct sockaddr_storage address;
^~~~~~~
-Kees
--
Kees Cook
Pixel Security
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