On Thu, Jan 30, 2020 at 11:23:38AM -0800, Kees Cook wrote:

Hm, looks like it's allocated from the low 16MB. Seems like poor naming!
:) There seems to be a LOT of stuff using GFP_DMA, and it seems unlikely
those are all expecting low addresses?

Most of that is either completely or partially bogus.  Besides the
weird S/390 stuff pretty much everything should be using the dma
allocators.  A couple really messed up drivers even pass GFP_DMA*
to the dma allocator, but my patches to fix that up seem to be stuck.