linux-kernel - Re: [patch 3/8] account user mounts

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Date:	Sun, 22 Apr 2007 10:08:49 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	ebiederm@...ssion.com
CC:	miklos@...redi.hu, akpm@...ux-foundation.org, serue@...ibm.com,
	viro@....linux.org.uk, linuxram@...ibm.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	containers@...ts.osdl.org
Subject: Re: [patch 3/8] account user mounts

> >> > From: Miklos Szeredi <mszeredi@...e.cz>
> >> >
> >> > Add sysctl variables for accounting and limiting the number of user
> >> > mounts.
> >> >
> >> > The maximum number of user mounts is set to 1024 by default.  This
> >> > won't in itself enable user mounts, setting a mount to be owned by a
> >> > user is first needed
> >> 
> >> Since each mount has a user can we just make this a per user rlimit?
> >> 
> >> If we are going to implement a sysctl at this point I think it should
> >> be a global limit that doesn't care if who you are.  Even root can
> >> have recursive mounts that attempt to get out of control.
> >
> > Recursive bind mounts are done carefully enough, so they don't get out
> > of control.
> >
> > Recursive mount propagations can get out of control.  But root can
> > shoot itself in the foot any number of ways, and it's not for the
> > kernel to police that.
> 
> Yes.  It is.
> 
> This is mostly about removing special cases.
> 
> We routinely have limits on resources that are global and apply
> to root along with every one else.  Root can change them but
> they still apply to root.  Things like the number of inodes
> in the system or the total number of files.

There's no max_inodes any more.  As for max_files:

get_empty_filp():

	/*
	 * Privileged users can go above max_files
	 */
	if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {

Miklos
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