On Thu, 6 Dec 2018 at 20:21, Andy Lutomirski [off-list ref] wrote:

On Thu, Dec 6, 2018 at 11:04 AM Ard Biesheuvel
[off-list ref] wrote:

quoted

On Thu, 6 Dec 2018 at 19:54, Andy Lutomirski [off-list ref] wrote:

quoted

quoted

quoted

That’s not totally nuts. Do we ever have code that expects __va() to
work on module data?  Perhaps crypto code trying to encrypt static
data because our APIs don’t understand virtual addresses.  I guess if
highmem is ever used for modules, then we should be fine.

The crypto code shouldn't care, but I think it will probably break hibernate :-(

How so?  Hibernate works (or at least should work) on x86 PAE, where
__va doesn't work on module data, and, on x86, the direct map has some
RO parts with where the module is, so hibernate can't be writing to
the memory through the direct map with its final permissions.

On arm64 at least, hibernate reads the contents of memory via the
linear mapping. Not sure about other arches.