[CFR] [PATCH] jail mount/unmount patch

[Pawel Jakub Dawidek]

On Wed, Jul 27, 2011 at 10:08:44PM +0200, Martin Matuska wrote:
> Please review my attached patch.
> 
> The patch fixes mount/unmount inside a jail for filesystems with the
> VFCF_JAIL flag
> security.jail.mount_allowed=1 is required.
> For "enforce_statfs == 2" it makes no sense to allow mount/unmount
> inside a jail so enforce_statfs == 2 implies mount_allowed = 0
> The filesystems mounted inside a jail have now a corect f_mntonname.
> 
> Tested with:
> zfs - works! (both enforce_statfs=0 and enforce_statfs=1)
> nullfs (with added VFCF_JAIL flag) - works ! (both enforce_statfs=0 and
> enforce_statfs=1)
> tmpfs (with added VFCF_JAIL flag) - works ! (both enforce_statfs=0 and
> enforce_statfs=1)
> 
> I assume other filesystems are going to work correctly, too (e.g nfs).
> Fore the future, I suggest a option to allow mounting specific
> filesystems in a jail (e.g. zfs, nullfs, tmpfs).
> 
> I consider nullfs mounts harmless inside a jail.
> 
> With jailed nullfs and tmpfs we can run tinderbox in a jail!

In you patch you depend on fact that full path to mount directory is
passed to the nmount(2) system call. This doesn't have to be true.
I changed mount(8) to call realpath(3) in mount directory, but I see no
reason someone calling nmount(2) directly with "./foo" mount dir.

I think the proper way is to build full path from within the kernel
using vn_fullpath_global().

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://yomoli.com
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