linux-kernel - Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped

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Message-ID: <20150114153323.GF2253@moon>
Date:	Wed, 14 Jan 2015 18:33:23 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	Calvin Owens <calvinowens@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Peter Feiner <pfeiner@...gle.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Siddhesh Poyarekar <siddhesh.poyarekar@...il.com>,
	linux-kernel@...r.kernel.org, kernel-team@...com,
	Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files

On Wed, Jan 14, 2015 at 05:25:01PM +0200, Kirill A. Shutemov wrote:
...
> > 
> > This gives lsof and suchlike a way to determine the pathnames of files
> > mapped into a process without incurring the O(N^2) behavior of the
> > maps file.
> 
> We already have /proc/PID/map_files/ directory which lists all mapped
> files. Should we consider relaxing permission checking there and move it
> outside CONFIG_CHECKPOINT_RESTORE instead?
> 
> Restriction to CAP_SYSADMIN for follow_link is undertansble, but why do we
> restrict readdir and readlink?

We didn't think this functionality might be needed someone but us (criu camp),
so that the rule of thumb was CONFIG_CHECKPOINT_RESTORE + CAP_SYSADMIN, until
otherwise strictly needed. So I think now we can relax security rules a bit
and allow to readdir and such for owners.

	Cyrill
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