From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Tejun Heo <tj@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrew Vagin <avagin@openvz.org>,
Serge Hallyn <serge.hallyn@canonical.com>,
Vasiliy Kulikov <segoon@openwall.com>,
Kees Cook <keescook@chromium.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Pavel Emelyanov <xemul@parallels.com>,
Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: [patch 3/3] [PATCH] prctl: Add PR_SET_MM codes to set up mm_struct entires v3
Date: Mon, 12 Dec 2011 17:24:56 -0500 [thread overview]
Message-ID: <4EE67F38.2030603@gmail.com> (raw)
In-Reply-To: <20111212215840.GS2199@moon>
(12/12/11 4:58 PM), Cyrill Gorcunov wrote:
> On Mon, Dec 12, 2011 at 04:49:38PM -0500, KOSAKI Motohiro wrote:
>> Hi
>>
>>> When we restore a task we need to set up text, data and data
>>> heap sizes from userspace to the values a task had at
>>> checkpoint time. This patch adds auxilary prctl codes for that.
>>>
>>> While most of them have a statistical nature (their values
>>> are involved into calculation of /proc/<pid>/statm output)
>>> the start_brk and brk values are used to compute an allowed
>>> size of program data segment expansion. Which means an arbitrary
>>> changes of this values might be dangerous operation. So to restrict
>>> access the following requirements applied to prctl calls:
>>>
>>> - The process has to have CAP_SYS_ADMIN capability granted.
>>
>> This is very dangerous feature and useless from regular admins.
>
> Except brk() call I don't see where it might be extremelly
> dangerous at moment but indeed it might become very dangerous
> once code grows. Still if evil minded person got CAP_SYS_ADMIN
> these prctls are least thing one should carry about.
I'm sorry, I misunderstood your code. Your code only allow to change
their own process attribute. So, it's enough harmless. Please ignore
my last mail.
>> Moreover, CAP_SYS_ADMIN has a pretty overweight meanings and
>> we can't disable it on practical. So, I have a question. Why
>> don't you make new capability for checkpoint?
>>
>
> It's not a problem to introduce CAP_CHECKPOINT_RESTORE, but
> would it be accepted? I mean, are we fine with new capability
> introduction? If yes -- I'll add new one and rebase the patch.
prev parent reply other threads:[~2011-12-12 22:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-12 20:06 [patch 0/3] Patches in a sake of checkpoint/restore, procfs and prctls Cyrill Gorcunov
2011-12-12 20:06 ` [patch 1/3] Kconfig: Introduce CHECKPOINT_RESTORE symbol Cyrill Gorcunov
2011-12-12 20:40 ` Kees Cook
2011-12-12 20:06 ` [patch 2/3] [PATCH] fs, proc: Add start_data, end_data, start_brk members to /proc/$pid/stat v4 Cyrill Gorcunov
2011-12-12 20:06 ` [patch 3/3] [PATCH] prctl: Add PR_SET_MM codes to set up mm_struct entires v3 Cyrill Gorcunov
2011-12-12 20:38 ` Kees Cook
2011-12-12 20:51 ` Cyrill Gorcunov
2011-12-12 21:53 ` Andrew Morton
2011-12-12 22:01 ` Cyrill Gorcunov
2011-12-12 22:05 ` Cyrill Gorcunov
2011-12-12 21:49 ` KOSAKI Motohiro
2011-12-12 21:58 ` Cyrill Gorcunov
2011-12-12 22:24 ` KOSAKI Motohiro [this message]
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