Re: [PATCH v5 2/2] staging: ion: create one device entry per heap

On 10/05/2017 06:06 AM, Benjamin Gaignard wrote:

2017-10-04 12:17 GMT+02:00 Mark Brown [off-list ref]:

quoted

On Tue, Oct 03, 2017 at 04:08:30PM -0700, Sandeep Patil wrote:

quoted

It is entirely possible and easy in android/ueventd to create those nodes
under "/dev/ion/".  (assuming the heap 'subsystem' for these new devices will
point to 'ion').

I think it is the same problem than for webcam under v4l framework.
Each time you plug a webcam you got a v4l node but android/uevent rules
the plug order doesn't have impact.
The same think will happen for ion nodes it may be even easier because
the heap will always being created in the smae order for a given product
configuration.

Relying on the heap being created in the same order seems troublesome.
If for some reason it changes in the kernel we might break something
in userspace.

Anyway, to move this forward I think we need to see a proof of concept
of using selinux to protect access to specific heaps.

Thanks,
Laura

quoted

The reason I didn't say /dev/ion/foo initially is that if people want to
keep the existing /dev/ion around for compatibility reasons then the
/dev/ion name isn't available which might cause issues.  Otherwise just
dumping everything under a directory (perhaps with a different name) was
my first thought as well.

quoted

(Also FWIW, the SELinux permissions are also possible with the current ion
implementation by adding rules to disallow specific ioctls instead of adding
permissions to access device node as this change would do)

AIUI the request is to limit access to specific heaps, and obviously not
everyone wants to deal with SELinux at all.