linux-kernel - Re: [PATCH v3] kernel: Conditionally support non-root users, groups and capabilities

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Date:	Sun, 8 Feb 2015 10:05:25 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Iulia Manda <iulia.manda21@...il.com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Josh Triplett <josh@...htriplett.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Tim Bird <tim.bird@...ymobile.com>
Subject: Re: [PATCH v3] kernel: Conditionally support non-root users, groups
 and capabilities

Hi Iulia,

On Fri, Feb 6, 2015 at 2:10 PM, Iulia Manda <iulia.manda21@...il.com> wrote:
> On 6 February 2015 at 02:03, Iulia Manda <iulia.manda21@...il.com> wrote:
>> There are a lot of embedded systems that run most or all of their functionality
>> in init, running as root:root. For these systems, supporting multiple users is
>> not necessary.
>>
>> This patch adds a new symbol, CONFIG_MULTIUSER, that makes support for non-root
>> users, non-root groups, and capabilities optional. It is enabled under
>> CONFIG_EXPERT menu.
>>
>> When this symbol is not defined, UID and GID are zero in any possible case
>> and processes always have all capabilities.
>>
>> The following syscalls are compiled out: setuid, setregid, setgid,
>> setreuid, setresuid, getresuid, setresgid, getresgid, setgroups, getgroups,
>> setfsuid, setfsgid, capget, capset.
>>
>> Also, groups.c is compiled out completely.
>>
>> This change saves about 25 KB on a defconfig build.
>>
>> The kernel was booted in Qemu. All the common functionalities work. Adding
>> users/groups is not possible, failing with -ENOSYS.
>>
>> Bloat-o-meter output:
>> add/remove: 7/87 grow/shrink: 19/397 up/down: 1675/-26325 (-24650)
>>
>
> Forgot to add:
>
> Signed-off-by: Iulia Manda <iulia.manda21@...il.com>
> Reviewed-by: Josh Triplett <josh@...htriplett.org>
>
>> ---
>> Changes since v2:
>>         - rename symbol;
>>         - make SECURITY dependent on MULTIUSER
>>
>
> + make symbols depend on MULTIUSER instead of selecting it.

Thanks for the update!

Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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