linux-kernel - Re: [GIT PULL] gcc-plugin updates for v4.19-rc1

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Date:   Wed, 15 Aug 2018 12:04:00 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Popov <alex.popov@...ux.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>,
        Mark Rutland <mark.rutland@....com>,
        Laura Abbott <labbott@...hat.com>,
        Will Deacon <will.deacon@....com>
Subject: Re: [GIT PULL] gcc-plugin updates for v4.19-rc1

On Wed, Aug 15, 2018 at 11:35 AM Kees Cook <keescook@...omium.org> wrote:
>
> I swear I'm doing my best. Are you speaking of
> stackleak_check_alloca() or stackleak_erase()? These were both
> discussed on the list, and we weren't able to come up with
> alternatives: in both cases we're off the stack, and recovery is
> seemingly impossible.

Why do you even *test* that thing? Why don't you just allocate stack
and clear it.

Dammit, the whole f*cking point of this patch-set is to clear the
stack used. It is *not* supposed to do anything else. If the process
runs out of stack, that's caught by the vmalloc'ed stack.

And if you don't  have vmalloc'ed stack, then clearly you don't care.

I refuse to take this kind of code that does stupid things, and then
*because* it does those initial stupid things it does even more stupid
things to correct for it.

I hated the thing to begin with, told people that there are better
approaches that don't have the downsides, got ignored, and then I'm
pushed crap.

No.

         Linus