linux-kernel - Re: [patch 00/10] mount ownership and unprivileged mount syscall (v8)

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Message-Id: <E1JSyFN-0003dA-0a@pomaz-ex.szeredi.hu>
Date:	Sat, 23 Feb 2008 18:33:13 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	viro@...IV.linux.org.uk
CC:	miklos@...redi.hu, hch@...radead.org, akpm@...ux-foundation.org,
	serue@...ibm.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, haveblue@...ibm.com
Subject: Re: [patch 00/10] mount ownership and unprivileged mount syscall (v8)

> On Mon, Feb 18, 2008 at 12:47:59PM +0100, Miklos Szeredi wrote:
> > So what should I do?
> > 
> > Would Al be wanting to merge this into his VFS tree?  (Can't find it
> > on git.kernel.org yet, BTW.)
> 
> FWIW, it's on hera right now, should propagate to git.kernel.org in a few.
> 
> Branches I'd pushed there: vfs-fixes.b0 and ro-bind.b0.  The latter is
> on top of the former.  There will be more, but that at least takes care
> of the most urgent stuff.  Again, apologies for things being too damn
> slow ;-/
> 
> As for the unprivileged mounts...
> 	a) why do we lose them on clone() in new namespace?  Bloody
> inconvenient, to put it mildly.
> 	b) why do we prohibit all kinds of remount?

I wanted to get the basics right, before thinking about these details.
But getting the semantics of a) right before this is merged is a good
idea, of course...  So I'll have to think about that.

The remount stuff can wait (especially if there will be a new mount
API for this kind of thing).

> 	c) just what is limited by that sysctl?  AFAICS, rbind is allowed
> if mountpoint is on user vfsmount and it seems to create vfsmounts without
> eating into that limit just fine...  What's the point of limiting the
> amount of vfsmounts marked user when you do not limit the number of vfsmount
> one can allocate?

The limit is there, so that unprivileged users cannot create insane
number of mounts.  It's just a safety thing, analogous to
/proc/sys/fs/file-max.

Thanks for looking at this.

Miklos
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