Messages in this thread | | | Date | Thu, 12 May 2016 10:31:42 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v8 1/4] x86/KASLR: Clarify identity map interface |
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* Kees Cook <keescook@chromium.org> wrote:
> 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. > */
Btw., is there any way to detect such invalid pointers during build-time somehow? This is not the first such bug and I suspect it won't be the last one either.
Thanks,
Ingo
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