linux-kernel - Re: [PATCH 14/16] vfs: Implement mount_super

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Message-ID: <87C89963-F554-481F-81FF-5DC395062943@zytor.com>
Date:	Tue, 19 Apr 2016 12:25:03 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	ebiederm@...ssion.com
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>, security@...ian.org,
	"security@...nel.org" <security@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"security@...ntu.com >> security" <security@...ntu.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Willy Tarreau <w@....eu>,
	Aurelien Jarno <aurelien@...el32.net>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Jann Horn <jann@...jh.net>, Greg KH <greg@...ah.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.com>, Florian Weimer <fw@...eb.enyo.de>
Subject: Re: [PATCH 14/16] vfs: Implement mount_super_once

On April 19, 2016 12:03:47 PM PDT, ebiederm@...ssion.com wrote:
>"H. Peter Anvin" <hpa@...or.com> writes:
>
>>>- Support for reserving ptys for the system devpts instance using
>>>  /proc/sys/kernel/pty/reserve needs to be removed.
>>>
>>>Eric
>>
>> pty capping should probably be a devpts mount option
>
>There is a max option so pty capping is a per devpts option.
>
>> , and perhaps a
>> sufficiently privileged user could be allowed to set another mount
>> option to allow that instance to dip into the reserved pool or exempt
>> it completely from the global limit as set in sysctl.
>
>I agree that we could keep the reserved pool, and add a new way to
>access it.  However no piece of existing userspace could use it.  So
>the
>simplest thing to do (unless something actually breaks), is to just
>remove the reserve pool.
>
>Eric

Perhaps a (privileged) option to exempt from the global limit, then.  Something we can implement if asked for.

However, I wouldn't be 100% that the reserved pool isn't used.  Someone added it presumably for a reason.  An administrator could say it and we'd have no idea.
-- 
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