linux-kernel - Re: [kernel-hardening] [PATCH v2 2/2] fork: make number of cached stacks (vmapped) configurable using Kbuild

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Message-ID: <20170209042629.GB4311@zzz>
Date:   Wed, 8 Feb 2017 20:26:29 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     Hoeun Ryu <hoeun.ryu@...il.com>
Cc:     Kees Cook <keescook@...omium.org>, Michal Marek <mmarek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Emese Revfy <re.emese@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Mickaël Salaün <mic@...ikod.net>,
        Nicholas Piggin <npiggin@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Mateusz Guzik <mguzik@...hat.com>,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: [kernel-hardening] [PATCH v2 2/2] fork: make number of cached
 stacks (vmapped) configurable using Kbuild

On Thu, Feb 09, 2017 at 01:03:47PM +0900, Hoeun Ryu wrote:
> +config NR_VMAP_STACK_CACHE
> +	int "Number of cached stacks"
> +	default "2"
> +	depends on VMAP_STACK
> +	help
> +	  This determines how many stacks can be cached for virtually
> +	  mapped kernel stacks.
> +

Can you explain in the help text under what circumstances someone should change
this, and to what value?  As-is, it seems like somewhat of a useless config
option which no one will ever change.

- Eric