linux-kernel - Re: [GIT PULL] usercopy fixes for v4.8-rc6

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Message-ID: <CAGXu5jKFFwk1zW9-xn0bJHZQYDGUdO=tAEC-bui4cMaEEomM-A@mail.gmail.com>
Date:   Wed, 7 Sep 2016 09:38:13 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [GIT PULL] usercopy fixes for v4.8-rc6

On Wed, Sep 7, 2016 at 9:33 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> Pulled, but:
>
> On Tue, Sep 6, 2016 at 12:37 PM, Kees Cook <keescook@...omium.org> wrote:
>>
>> Kees Cook (3):
>>       usercopy: fold builtin_const check into inline function
>
> Hmm. So with this, check_object_size() seems sane, but it's only
> marked "inline".
>
> And we've had the issue that without the __always_inline, gcc will
> randomly not inline things. In fact, this very pull added that to the

Yeah, reading the thread from 2009 made my head spin. :(

> copy_xyz_user() functions exactly because of this issue.
>
> Now, it may be that check_object_size() is so simple that it really
> always *will* be inlined regardless, but it looks a bit dodgy.

True, yes. I will send another update with that added.

(And a heads-up: another part of the update will be the disabling
hardened usercopy's page-spanning checker too -- we've had another
false positive hit on that, so it's time to drop it.)

Thanks!

-Kees

-- 
Kees Cook
Nexus Security