linux-kernel - Re: [PATCH] sgi-xp: use designated initializers

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Date:   Sat, 6 May 2017 00:16:02 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Robin Holt <robinmholt@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, Cliff Whickman <cpw@....com>
Subject: Re: [PATCH] sgi-xp: use designated initializers

On Wed, Mar 29, 2017 at 1:48 PM, Kees Cook <keescook@...omium.org> wrote:
> On Tue, Jan 3, 2017 at 3:19 PM, Kees Cook <keescook@...omium.org> wrote:
>> On Wed, Dec 21, 2016 at 8:24 AM, Robin Holt <robinmholt@...il.com> wrote:
>>> On Fri, Dec 16, 2016 at 7:01 PM, Kees Cook <keescook@...omium.org> wrote:
>>>> Prepare to mark sensitive kernel structures for randomization by making
>>>> sure they're using designated initializers. These were identified during
>>>> allyesconfig builds of x86, arm, and arm64, with most initializer fixes
>>>> extracted from grsecurity.
>>>
>>> I guess I don't understand the context enough here to give you a
>>> Signed-off-by.  Can you give us more background on this randomization?
>>
>> Sure thing! The randomization is on the order of function pointers in
>> all-pointer structures (like struct xpc_interface). As long as the
>> memory containing the structure isn't shared externally, this
>> randomization should have no operational effect. The reason explicit
>> no-op functions were added was to avoid ugly casts, etc.
>
> Friendly ping ... any chance this can land in -next soon?
>
>>> From what I see in the code here, I can see you are providing
>>> equivalent functionality and I would give it a signed-off-by, but I am
>>> not sure this randomization of which you speak is not going to cause
>>> problems for XP, XPC, XPNET, and XPMEM (out of tree GPL kernel
>>> module).
>>
>> Ah, hm, does this module share the structure without being built
>> against the kernel? (If built with the kernel, the randomization
>> plugin will keep things in the right order.)
>
> Regardless of your answer, this randomization can be turned off.
> Switching to designated initializers here is mainly just a clean up.

Any thoughts on this? I'd love to get this landed, and I'm happy to
carry the patch myself, if it helps. Anyone able to Ack?

Thanks!

-Kees

-- 
Kees Cook
Pixel Security