Date: Mon, 7 Aug 2017 17:01:14 -0700 From: Kees Cook <keescook@...omium.org> To: "Gustavo A. R. Silva" <gustavo@...eddedor.com> Cc: Thomas Garnier <thgarnie@...gle.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com> Subject: Re: I want to help out On Mon, Aug 7, 2017 at 4:35 PM, Gustavo A. R. Silva <gustavo@...eddedor.com> wrote: > Yeah, this has to do with the use __ro_after_init for the case of .ctors > (.init_array) ELF section. > > The case of .dtors or .fini_array ELF section is similar. A heap overflow > could overwrite a .fini_array function pointer. But I guess this could be > detected by guard pages. Oh, hm, I would have expected all of those to be entirely read-only already. How does the kernel use those dynamically? > So, I guess the idea would be to follow this same approach: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e37e43a497d5a8b7c0cc1736d56986f432c394c9 > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=13d4ea097d18b419ad2a2b696063d44bf59acec0 > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c65eacbe290b8141554c71b2c94489e73ade8c8d > > right? As far as I know, yes. > What would be a good strategy to start tackling those tasks? I suspect the arm64 folks here may have suggestions about how to do either on arm. I would expect moving addr_limit off the stack to mainly be moving the structure and dealing with the header fallout and syscall entry/exit assembly. For VMAP_STACK, I think there is a lot of other work to handle faults correctly. -Kees -- Kees Cook Pixel Security
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