Re: [RFC][PATCH] sysctl: Remove the sysctl system call

From: Kees Cook <keescook@chromium.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
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	Anders Berg <anders.berg@lsi.com>,
	Apelete Seketeli <apelete@seketeli.net>,
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	Chee Nouk Phoon <cnphoon@altera.com>,
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	Santosh Shilimkar <santosh.shilimkar@ti.com>,
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	Stephen Boyd <sboyd@codeaurora.org>,
	"Steven J. Hill" <Steven.Hill@imgtec.com>,
	Tanmay Inamdar <tinamdar@apm.com>,
	Vineet Gupta <vgupta@synopsys.com>
Subject: Re: [RFC][PATCH] sysctl: Remove the sysctl system call
Date: Tue, 1 Oct 2019 11:46:45 -0700	[thread overview]
Message-ID: <201910011140.EA0181F13@keescook> (raw)
In-Reply-To: <8736gcjosv.fsf@x220.int.ebiederm.org>

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