Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files

From: Cyrill Gorcunov <gorcunov@gmail.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Calvin Owens <calvinowens@fb.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Peter Feiner <pfeiner@google.com>,
	Grant Likely <grant.likely@secretlab.ca>,
	Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>,
	linux-kernel@vger.kernel.org, kernel-team@fb.com,
	Pavel Emelyanov <xemul@openvz.org>
Subject: Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files
Date: Wed, 14 Jan 2015 18:33:23 +0300	[thread overview]
Message-ID: <20150114153323.GF2253@moon> (raw)
In-Reply-To: <20150114152501.GB9820@node.dhcp.inet.fi>

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