linux-kernel - Re: [tip:x86/mm] x86/mmap, ASLR: Do not treat unlimited-stack tasks as legacy mmap

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Message-ID: <20170623145441.GB9388@redhat.com>
Date:   Fri, 23 Jun 2017 16:54:41 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     tip-bot for Michal Hocko <tipbot@...or.com>
Cc:     linux-tip-commits@...r.kernel.org, torvalds@...ux-foundation.org,
        mingo@...nel.org, hpa@...or.com, jkosina@...e.cz, mhocko@...e.com,
        tglx@...utronix.de, davej@...emonkey.org.uk, peterz@...radead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [tip:x86/mm] x86/mmap, ASLR: Do not treat unlimited-stack tasks
 as legacy mmap

On 06/23, tip-bot for Michal Hocko wrote:
>
> We added a heuristics to treat applications with RLIMIT_STACK configured
> to unlimited as legacy. This means:

To me this also means a minor security problem. The comment above
PER_CLEAR_ON_SETID says "must be cleared upon setuid or setgid exec",
but if you do "ulimit -s unlimited" before suid exec then
ADDR_COMPAT_LAYOUT set by security checks will be ignored.

> So let's try and remove this assumption - hopefully nothing breaks.

Agreed.

Oleg.