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

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Date:   Fri, 19 Jan 2018 14:49:20 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.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: [PATCH 0/3] exec: Pin stack limit during exec

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