Messages in this thread | | | Date | Wed, 11 May 2016 08:23:45 -0700 | Subject | Re: [PATCH v8 1/4] x86/KASLR: Clarify identity map interface | From | Kees Cook <> |
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On Tue, May 10, 2016 at 11:24 PM, Ingo Molnar <mingo@kernel.org> wrote: > > * Kees Cook <keescook@chromium.org> wrote: > >> +/* >> + * Mapping information structure passed to kernel_ident_mapping_init(). >> + * Due to relocation, pointers must be assigned at run time not build time. >> + */ >> +static struct x86_mapping_info mapping_info = { >> + .pmd_flag = __PAGE_KERNEL_LARGE_EXEC, >> +}; > >> +void initialize_identity_maps(void) >> { >> + /* Init mapping_info with run-time function/buffer pointers. */ >> + mapping_info.alloc_pgt_page = alloc_pgt_page; >> + mapping_info.context = &pgt_data; > > Could you please outline the precise failure mode? What gets executed when, which > pointer gets relocated and which not, and exactly when does it pose a problem, > etc.
It's the issue described at the top of misc.c:
/* * WARNING!! * This code is compiled with -fPIC and it is relocated dynamically at * run time, but no relocation processing is performed. This means that * it is not safe to place pointers in static structures. */
Should this be repeated in each .c file maybe as a reminder?
If the rest of the patches look good, we could clean this up as a following patch? What do you think?
-Kees
-- Kees Cook Chrome OS & Brillo Security
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