linux-kernel - Re: [PATCH 4/7] seccomp_filter: add process state reporting

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Date:	Wed, 27 Apr 2011 22:43:04 -0500
From:	Will Drewry <wad@...omium.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, kees.cook@...onical.com,
	eparis@...hat.com, agl@...omium.org, mingo@...e.hu,
	jmorris@...ei.org, rostedt@...dmis.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	David Howells <dhowells@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Stephen Wilson <wilsons@...rt.ca>
Subject: Re: [PATCH 4/7] seccomp_filter: add process state reporting

On Wed, Apr 27, 2011 at 10:40 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Wed, Apr 27, 2011 at 10:24:20PM -0500, Will Drewry wrote:
>
>> Definitely.  Would it make sense to have /proc/<pid>/seccomp and
>> /proc/<pid>/seccomp_filter?
>
> Just one question: WTF bother with S_IRUSR?  Note that it's absolutely
> _useless_ in procfs; any kind of permission checks must be done in
> read(2) time since doing it in open(2) is worthless.  Consider execve()
> on suid binary; oops, there goes your uid and there goes the effect
> of checks done by open(2).  And if you *do* checks in read(2), why bother
> duplicating them in open(2)?

In earlier versions I was allowing filter/bitmask updating via the
proc file (which I nixed :).  Is S_IRUGO preferred? I don't see any
crazy information leakage by sharing the filters/ruleset.  I'll fold
it into the next version of this patch.

thanks!
will
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