Re: Mislabeled /proc/<pid>/ns/mnt files?

[Dominick Grift <dac.override@gmail.com>]

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On Thu, May 09, 2019 at 02:47:30PM -0700, Jeffrey Vander Stoep wrote:
> From: Stephen Smalley <sds@tycho.nsa.gov>
> Date: Thu, May 9, 2019 at 2:17 PM
> To: Jeffrey Vander Stoep, <selinux@vger.kernel.org>, Joel Galenson,
> Petr Lautrbach
> 
> > On 5/9/19 3:56 PM, Jeffrey Vander Stoep wrote:
> > > I expected files here would have the process's context, but they
> > > don't. The files are actually all symlinks so it's entirely possible
> > > that the they shouldn't have the process's context. If that's the
> > > case, how can I provide different labels for them? Neither "proc" nor
> > > "unlabeled" are appropriate.
> > >
> > > On a device with a 3.18 kernel they have the "proc" context:
> > > sailfish:/ # ls -LZ1 /proc/1/ns
> > > u:object_r:proc:s0 mnt
> > > u:object_r:proc:s0 net
> > >
> > > On a device with the 4.9 kernel the have the "unlabeled" context:
> > > blueline:/ # ls -LZ1 /proc/1/ns
> > > u:object_r:unlabeled:s0 cgroup
> > > u:object_r:unlabeled:s0 mnt
> > > u:object_r:unlabeled:s0 net
> >
> > First, ls -L dereferences symlinks so you are going to get the context
> > of the object referenced by the symlink, not the context of the symlink
> > itself.
> 
> I'm seeing a denial on the object not the symlink, so -L is what I want.
> 
> >
> > Second, the task context is only assigned to proc inodes created via
> > proc_pid_make_inode(), which has never been the case of /proc/pid/ns
> > inodes - those have their own implementations and operations.
> >
> > Third, /proc/pid/ns migrated from proc to its own pseudo filesystem,
> > nsfs, which requires a corresponding fs_use or genfscon rule in policy
> > or they will be unlabeled.  refpolicy has a genfscon rule. Confusingly
> > there appears to be both in Fedora policy, a fs_use_task and a genfscon
> > rule, and it appears that fs_use_task is being applied here.  I don't
> > know why or what exactly that means.  It won't be the task context for
> > the task associated with that /proc/pid directory but instead would be
> > whichever task context instantiates the inode.
> >
> 
> So, how do I label these files in genfs_contexts?
> 
> "mount | grep nsfs" returns nothing.

# seinfo --genfs | grep nsfs
   genfscon nsfs /  sys.id:sys.role:fs.nsfs.fs:s0

Yes, i think this is a step backwards. In the past we got a nice list of objects that have no context associated when policy is loaded.
That list was removed. So sometimes its hard to determine whether something needs a genfscon if its not listen with `mount.

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Dominick Grift

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