The Intel 965 and above chipsets moved the batch buffer security bit to
another place, this means the current DRM allows commands that can touch
any part of main memory to be submitted on those chipsets. The user
requires to be logged onto a local X server and have access to the drm.
a) which users typically have access to the drm? Anyone?
There is an xorg config option to set the permissions, but typically
only the logged in user on the primary X server can actually do anything
as there is a separate authentication processes, so usually the user
already has physical access at that point..
b) what actually can they do with it? Modify arbitrary physical
addresses with user-provided data? Or something less bad?
Transfer user data to any physcial memory address...
The documentation required to actually exploit this bug isn't publicly