linux-kernel - Re: [RFC, PATCHv2 29/29] mm, x86: introduce RLIMIT

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Date:   Wed, 04 Jan 2017 14:55:41 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Andy Lutomirski <luto@...capital.net>,
        linux-arch <linux-arch@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Linux API <linux-api@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Will Deacon <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC, PATCHv2 29/29] mm, x86: introduce RLIMIT_VADDR

On Tuesday, January 3, 2017 2:09:16 PM CET Andy Lutomirski wrote:
> >
> >> When
> >> ADDR_LIMIT_EXPLICIT is in effect, prctl can set a 64-bit numeric
> >> limit.  If ADDR_LIMIT_EXPLICIT is cleared, the prctl value stops being
> >> settable and reading it via prctl returns whatever is implied by the
> >> other personality bits.
> >
> > I don't see anything wrong with it, but I'm a bit confused now
> > what this would be good for, compared to using just prctl.
> >
> > Is this about setuid clearing the personality but not the prctl,
> > or something else?
> 
> It's to avid ambiguity as to what happens if you set ADDR_LIMIT_32BIT
> and use the prctl.  ISTM it would be nice for the semantics to be
> fully defined in all cases.
> 

Ok, got it.

	Arnd