Report from Olof Johansson:
On PPC970, having HID0 (en_attn) set makes it possible to wedge the machine
by just doing an 'asm volatile("attn");' from userspace, clearly a local DoS
exposure. Apple firmware seems to set it and we don't clear it at boot time.
I'm not aware of any intentional exploits of this. I happened to come across it
by running crash01 from LTP, it tries to execute random data as code and kept
locking up my machine.
Created attachment 133779 [details]
Proposed patch from Olof Johansson
committed in stream E5 build 42.0.3
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release. Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products. This request is not yet committed for inclusion in an Update
committed in stream U5 build 42.14. A test kernel with this patch is available
QE ack for 4.5.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.