RE: [PATCH v5 23/39] mm: Don't allow write GUPs to shadow stack memory
From: Schimpe, Christina <hidden>
Date: 2023-01-25 15:36:35
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On Tue, 2023-01-24 at 17:26 +0100, David Hildenbrand wrote:quoted
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Isn't it possible to overwrite GOT pointers using the same vector? So I think it's merely reflecting the status quo.There was some debate on this. /proc/self/mem can currently write through read-only memory which protects executable code. So should shadow stack get separate rules? Is ROP a worry when you can overwrite executable code?The question is, if there is reasonable debugging reason to keep it. I assume if a debugger would adjust the ordinary stack, it would have to adjust the shadow stack as well (oh my ...). So it sounds reasonable to have it in theory at least ... not sure when debugger would support that, but maybe they already do.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.
Our patches for GDB use /proc/PID/mem to read/write shadow stack memory. However, I think it should be possible to change this to ptrace but GDB normally uses /proc/PID/mem to read/write target memory. Regards, Christina Intel Deutschland GmbH Registered Address: Am Campeon 10, 85579 Neubiberg, Germany Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de> Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva Chairperson of the Supervisory Board: Nicole Lau Registered Office: Munich Commercial Register: Amtsgericht Muenchen HRB 186928