| Date | Mon, 23 Jan 2023 10:10:04 +0100 | Subject | Re: [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory | From | David Hildenbrand <> |
| |
On 19.01.23 22:23, Rick Edgecombe wrote: > The x86 Control-flow Enforcement Technology (CET) feature includes a new > type of memory called shadow stack. This shadow stack memory has some > unusual properties, which requires some core mm changes to function > properly. > > Shadow stack memory is writable only in very specific, controlled ways. > However, since it is writable, the kernel treats it as such. As a result > there remain many ways for userspace to trigger the kernel to write to > shadow stack's via get_user_pages(, FOLL_WRITE) operations. To make this a > little less exposed, block writable GUPs for shadow stack VMAs. > > Still allow FOLL_FORCE to write through shadow stack protections, as it > does for read-only protections.
So an app can simply modify the shadow stack itself by writing to /proc/self/mem ?
Is that really intended? Looks like security hole to me at first sight, but maybe I am missing something important.
-- Thanks,
David / dhildenb
|