Re: [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory
From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Date: 2023-01-24 23:41:23
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Possibly related (same subject, not in this thread)
- 2023-01-23 · Re: [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory · David Hildenbrand <hidden>
- 2023-01-19 · [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory · Rick Edgecombe <rick.p.edgecombe@intel.com>
On Tue, 2023-01-24 at 15:08 -0800, Kees Cook wrote:
quoted
GDB support for shadow stack is queued up for whenever the kernel interface settles. I believe it just uses ptrace, and not this proc. But yea ptrace poke will still need to use FOLL_FORCE and be able to write through shadow stacks.I'd prefer to avoid adding more FOLL_FORCE if we can. If gdb can do stack manipulations through a ptrace interface then let's leave off FOLL_FORCE.
Ptrace and /proc/self/mem both use FOLL_FORCE. I think ptrace will always need it or something like it for debugging. To jog your memory, this series doesn't change what uses FOLL_FORCE. It just sets the shadow stack rules to be the same as read-only memory. So even though shadow stack memory is sort of writable, it's a bit more locked down and FOLL_FORCE is required to write to it with GUP. If we just remove FOLL_FORCE from /proc/self/mem, something will probably break right? How do we do this? Some sort of opt-in?