linux-kernel - Re: [RFC][PATCH] sysctl: Remove the sysctl system call

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Message-ID: <201910011140.EA0181F13@keescook>
Date:   Tue, 1 Oct 2019 11:46:45 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-api@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andi Kleen <andi@...stfloor.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Alex Smith <alex.smith@...tec.com>,
        Anders Berg <anders.berg@....com>,
        Apelete Seketeli <apelete@...eteli.net>,
        Arnd Bergmann <arnd@...db.de>,
        Chee Nouk Phoon <cnphoon@...era.com>,
        Chris Zankel <chris@...kel.net>,
        Christian Ruppert <christian.ruppert@...lis.com>,
        Greg Ungerer <gerg@...inux.org>,
        Harvey Hunt <harvey.hunt@...tec.com>,
        Helge Deller <deller@....de>, Hongliang Tao <taohl@...ote.com>,
        Hua Yan <yanh@...ote.com>, Huacai Chen <chenhc@...ote.com>,
        John Crispin <blogic@...nwrt.org>,
        Jonas Jensen <jonas.jensen@...il.com>,
        Josh Boyer <jwboyer@...il.com>, Jun Nie <jun.nie@...aro.org>,
        Kevin Hilman <khilman@...aro.org>,
        Kevin Wells <kevin.wells@....com>,
        Kumar Gala <galak@...eaurora.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Ley Foon Tan <lftan@...era.com>,
        Linus Walleij <linus.walleij@...aro.org>,
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        Max Filippov <jcmvbkbc@...il.com>,
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        Paul Burton <paul.burton@...s.com>,
        Paul Mundt <lethal@...ux-sh.org>,
        Phil Edworthy <phil.edworthy@...esas.com>,
        Pierrick Hascoet <pierrick.hascoet@...lis.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Roland Stigge <stigge@...com.de>,
        Santosh Shilimkar <santosh.shilimkar@...com>,
        Scott Telford <stelford@...ence.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        "Steven J. Hill" <Steven.Hill@...tec.com>,
        Tanmay Inamdar <tinamdar@....com>,
        Vineet Gupta <vgupta@...opsys.com>
Subject: Re: [RFC][PATCH] sysctl: Remove the sysctl system call

On Tue, Oct 01, 2019 at 01:36:32PM -0500, Eric W. Biederman wrote:
> 
> This system call has been deprecated almost since it was introduced, and
> in a survey of the linux distributions I can no longer find any of them
> that enable CONFIG_SYSCTL_SYSCALL.  The only indication that I can find
> that anyone might care is that a few of the defconfigs in the kernel
> enable CONFIG_SYSCTL_SYSCALL.  However this appears in only 31 of 414
> defconfigs in the kernel, so I suspect this symbols presence is simply
> because it is harmless to include rather than because it is necessary.
> 
> As there appear to be no users of the sysctl system call, remove the
> code.  As this removes one of the few uses of the internal kernel mount
> of proc I hope this allows for even more simplifications of the proc
> filesystem.

I'm for it. :) I tripped over this being deprecated over a decade ago. :P

I think you can actually take this further and remove (or at least
empty) the uapi/linux/sysctl.h file too.

-- 
Kees Cook