linux-kernel - Re: [kernel-hardening] Re: [PATCH 0/3] exec: Pin stack limit during exec

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Message-Id: <8BCDD560-66F5-4CF7-97DD-E2E5BE1D13F4@nullcore.net>
Date:   Fri, 19 Jan 2018 20:12:40 -0500
From:   David Windsor <dave@...lcore.net>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Ben Hutchings <ben@...adent.org.uk>, Willy Tarreau <w@....eu>,
        Hugh Dickins <hughd@...gle.com>,
        Oleg Nesterov <oleg@...hat.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...hat.com>,
        Laura Abbott <labbott@...hat.com>, Greg KH <greg@...ah.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linux-MM <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com
Subject: Re: [kernel-hardening] Re: [PATCH 0/3] exec: Pin stack limit during exec

I have some spare cycles; is there any more relevant information outside of this thread?

Thanks,
David

> On Jan 19, 2018, at 5:49 PM, Kees Cook <keescook@...omium.org> wrote:
> 
>> On Tue, Jan 9, 2018 at 12:23 PM, Kees Cook <keescook@...omium.org> wrote:
>> Attempts to solve problems with the stack limit changing during exec
>> continue to be frustrated[1][2]. In addition to the specific issues
>> around the Stack Clash family of flaws, Andy Lutomirski pointed out[3]
>> other places during exec where the stack limit is used and is assumed
>> to be unchanging. Given the many places it gets used and the fact that
>> it can be manipulated/raced via setrlimit() and prlimit(), I think the
>> only way to handle this is to move away from the "current" view of the
>> stack limit and instead attach it to the bprm, and plumb this down into
>> the functions that need to know the stack limits. This series implements
>> the approach. I'd be curious to hear feedback on alternatives.
> 
> Friendly ping -- looking for some people with spare cycles to look
> this over. If people want, I can toss it into -next as part of my kspp
> tree. It's been living happily in 0-day for  2 weeks...
> 
> Thanks!
> 
> -Kees
> 
>> [1] 04e35f4495dd ("exec: avoid RLIMIT_STACK races with prlimit()")
>> [2] 779f4e1c6c7c ("Revert "exec: avoid RLIMIT_STACK races with prlimit()"")
>> [3] to security@...nel.org, "Subject: existing rlimit races?"
> 
> -- 
> Kees Cook
> Pixel Security