Re: [PATCH-RFC] code for raceless /sys/fs/foofs/*

[viro@parcelfarce.linux.theplanet.co.uk]

On Wed, May 05, 2004 at 05:28:03PM +0100, viro@parcelfarce.linux.theplanet.co.uk wrote:
> On Wed, May 05, 2004 at 05:53:16PM +0400, Nikita Danilov wrote:
> > Hello,
> > 
> > attached patch adds code necessary to safely export per-super-block
> > information in /sys/fs and /proc/fs.
> > 
> > Common problem with exporting file system information in procfs or sysfs
> > is a race between method that inputs/outputs data and concurrent umount
> > of the super-block involved.
>  
> Aside of the implementation questions (will comment later), there is an
> interface problem here.  We end up allowing anyone who has sysfs mounted
> (in chroot jail, in limited namespace, etc.) to pin down _any_ reiser4
> superblock, whether they have the thing itself mounted or not.

[sorry about truncated message - -ENOCOFFEE hits]

We also allow anyone with sysfs mounted to see which filesystems are currently
mounted on the box - again, regardless of being able to see them in the
chroot jail/restricted namespace/etc.  It can easily become an issue in
setups where such information is sensitive.