[MODERATED] Re: [PATCH v6 31/43] MDSv6

[Andi Kleen <ak@linux.intel.com>]

On Mon, Feb 25, 2019 at 04:19:35PM +0100, speck for Greg KH wrote:
> On Sun, Feb 24, 2019 at 07:07:37AM -0800, speck for Andi Kleen wrote:
> > From: Andi Kleen <ak@linux.intel.com>
> > Subject:  mds sweep: Clear cpu for usbmon intercepts
> > 
> > usbmon touches user data in interrupts that otherwise don't
> > touch user data. Automatically schedule a clear cpu if
> > usbmon is called from an interrupt.
> 
> I have written a long and very satisfying rant about this patch, that I
> than deleted, as it made me feel very better, but probably would not
> have helped anyone else out.
> 
> In turn, I need you to properly justify this patch as these two tiny
> sentences, and this small patch make no sense to me at all.  Please
> explain _WHY_ this is needed in this specific location.  Before
> responding, I would strongly recommend reading up on exactly what usbmon
> is and who is allowed to use it.  If after doing that, you still feel

Right it's root only.

But this is not about leaking data to the root monitoring user
(who can see the data anyways), but to unrelated processes
which are not root, but happen to be interrupted by the USB
interrupt.

> this patch is needed (and it might be, I still can not tell for sure),

Anything that touches user data in an interrupt needs to be marked
with the lazy approach.

I can write more on this instance.

However I will probably not be able to write a detailed
description for each of the interrupt handlers changed because
there are just too many.

-Andi