LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: hch@infradead.org, akpm@linux-foundation.org, serue@us.ibm.com,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	haveblue@us.ibm.com
Subject: Re: [patch 00/10] mount ownership and unprivileged mount syscall (v8)
Date: Sat, 23 Feb 2008 18:57:01 +0000	[thread overview]
Message-ID: <20080223185701.GS27894@ZenIV.linux.org.uk> (raw)
In-Reply-To: <E1JSyFN-0003dA-0a@pomaz-ex.szeredi.hu>

On Sat, Feb 23, 2008 at 06:33:13PM +0100, Miklos Szeredi wrote:
> > 	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.

Can't they?  Looks like one can create any number of vfsmounts without
getting more than one marked MNT_USER...

What are you trying to limit - vfsmounts or superblocks?  The former is
not limited in your patchset at all, AFAICS - you can
do while true; do
	mount --bind /bin ~/my_directory;
	mount --bind /sbin ~/my_directory;
done
indefinitely and all the bleeding stack of vfsmounts will be !MNT_USER.
Or any number of similar schemes, really, without overmounting if you
wish to avoid it.

If you are trying to limit the number of superblocks (i.e. active instances
of filesystems), then I'd say that vfsmounts make piss-poor proxies for
those and it would be better to count the objects you really want to count...

  reply	other threads:[~2008-02-23 18:57 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-05 21:36 Miklos Szeredi
2008-02-05 21:36 ` [patch 01/10] unprivileged mounts: add user mounts to the kernel Miklos Szeredi
2008-02-05 21:36 ` [patch 02/10] unprivileged mounts: allow unprivileged umount Miklos Szeredi
2008-02-05 21:36 ` [patch 03/10] unprivileged mounts: propagate error values from clone_mnt Miklos Szeredi
2008-02-05 21:36 ` [patch 04/10] unprivileged mounts: account user mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 05/10] unprivileged mounts: allow unprivileged bind mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 06/10] unprivileged mounts: allow unprivileged mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 07/10] unprivileged mounts: add sysctl tunable for "safe" property Miklos Szeredi
2008-02-06 20:21   ` Serge E. Hallyn
2008-02-06 21:11     ` Miklos Szeredi
2008-02-06 22:45       ` Serge E. Hallyn
2008-02-07  8:09         ` Miklos Szeredi
2008-02-07 14:05           ` Serge E. Hallyn
2008-02-07 14:36             ` Miklos Szeredi
2008-02-07 16:57               ` Serge E. Hallyn
2008-02-07 15:33   ` Aneesh Kumar K.V
2008-02-07 16:24     ` Miklos Szeredi
2008-02-05 21:36 ` [patch 08/10] unprivileged mounts: make fuse safe Miklos Szeredi
2008-02-05 21:36 ` [patch 09/10] unprivileged mounts: propagation: inherit owner from parent Miklos Szeredi
2008-02-05 21:36 ` [patch 10/10] unprivileged mounts: add "no submounts" flag Miklos Szeredi
2008-02-15  6:21 ` [patch 00/10] mount ownership and unprivileged mount syscall (v8) Andrew Morton
2008-02-15  9:01   ` Christoph Hellwig
2008-02-15  9:09     ` Andrew Morton
2008-02-15  9:14       ` Christoph Hellwig
2008-02-18 11:47         ` Miklos Szeredi
2008-02-23 16:09           ` Al Viro
2008-02-23 17:33             ` Miklos Szeredi
2008-02-23 18:57               ` Al Viro [this message]
2008-02-23 19:48                 ` Miklos Szeredi

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080223185701.GS27894@ZenIV.linux.org.uk \
    --to=viro@zeniv.linux.org.uk \
    --cc=akpm@linux-foundation.org \
    --cc=haveblue@us.ibm.com \
    --cc=hch@infradead.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=miklos@szeredi.hu \
    --cc=serue@us.ibm.com \
    --subject='Re: [patch 00/10] mount ownership and unprivileged mount syscall (v8)' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).