linux-kernel - Re: [PATCH 2/2] x86/mmap: handle worst-case heap randomization in mmap

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Message-ID: <34381CFC-A90F-4979-9802-2BA0E6539C68@amazon.com>
Date:   Mon, 15 Apr 2019 16:03:34 +0000
From:   "Saidi, Ali" <alisaidi@...zon.com>
To:     Kees Cook <keescook@...omium.org>, Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Jann Horn <jannh@...gle.com>
CC:     Dave Hansen <dave.hansen@...ux.intel.com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        X86 ML <x86@...nel.org>, Will Deacon <will.deacon@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/2] x86/mmap: handle worst-case heap randomization in
 mmap_base



On 3/27/19, 2:52 PM, "linux-arm-kernel on behalf of Kees Cook" <linux-arm-kernel-bounces@...ts.infradead.org on behalf of keescook@...omium.org> wrote:

    Adding some more people to CC... what do people think about this
    moving of the brk to ELF_ET_DYN_BASE in this corner-case? Anything
    that worked before should still work (i.e. the ultimately-launched
    binary already had the brk very far from its text, so this should be
    no different from a COMPAT_BRK standpoint). The only risk I see here
    is that if someone started to suddenly depend on the entire memory
    space above the mmap region being available when launching binaries
    via a direct loader execs... which seems highly unlikely, I'd hope:
    this would mean a binary would not work when execed normally.

Kees' proposal addresses the issue for me. Anyone have concerns on this proposed solution?

Ali