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

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Date:   Wed, 13 Mar 2019 09:25:38 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Ali Saidi <alisaidi@...zon.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, x86@...nel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Anthony Liguori <aliguori@...zon.com>
Subject: Re: [PATCH 2/2] x86/mmap: handle worst-case heap randomization in
 mmap_base

On 3/12/19 10:32 AM, Ali Saidi wrote:
> +	/* Provide space for brk randomization */
> +	pad += SZ_32M;

Just curious:  Why is the padding in your other patch conditional on the
32-bit vs. 64-bit apps, but here it's always 32M?

Also, did you hit this problem in practice somehow?