[PATCH 2/4] pid: Export find_task_by_vpid for use in external modules

Russell King - ARM Linux [off-list ref] writes:

On Thu, May 10, 2018 at 01:39:18PM -0600, Mathieu Poirier wrote:

quoted

Hi Russell,

On 10 May 2018 at 02:40, Russell King - ARM Linux [off-list ref] wrote:

quoted

This does not leak information from other namespaces because of the
uniqueness of the global PID.  However, what it does leak is the value
of the global PID which is meaningless in the namespace.  So, before
the event stream is delivered to userspace, this value needs to be
re-written to the namespace's PID value.

Unfortunately that can't be done.  The trace stream is compressed and
needs to be decompressed using an external library.  I think the only
option is to return an error if a user is trying to use this feature
from a namespace.

That sounds like a sensible approach, and that should get rid of the
vpid stuff too.

Eric, would this solve all your concerns?

It does, and I have given my ack to the respin.

I am moderately concerned about using the global pid with hardware.  But
pids are a core abstraction that aren't going anywhere.  As long as
hardware does not impose constraints on pids that software already does
not we should be fine.

Eric