Messages in this thread | | | Date | Mon, 01 Jul 2013 09:35:20 -0700 | From | Arjan van de Ven <> | Subject | Re: [PATCH] x86, kernel: make dump_pagetables a tristate |
| |
On 7/1/2013 8:55 AM, Kees Cook wrote: > On Mon, Jul 1, 2013 at 6:58 AM, Arjan van de Ven <arjan@linux.intel.com> wrote: >> On 6/29/2013 9:05 PM, Kees Cook wrote: >>> >>> Being able to examine page tables is handy, so make this a module that >>> can be loaded as needed. >> >> I personally don't think this is a good idea due to the various >> security/etc implications of this feature... should really just >> be off for non-debug kernels, not "off unless you load the module" > > I struggled with this too, but I couldn't come up with any reason that > made sense. If a system is running without modules_disabled, this code > is still loadable: > https://www.outflux.net/blog/archives/2011/04/27/non-executable-kernel-memory-progress/ > > The root user just needs to look at /proc/kallsyms before passing an > argument. So having it NOT a tristate doesn't actually change anything > except make it awkward to get it done. > > If a system is running with verified modules, then just not > signing/including ptdump makes it unavailable. And running with > modules_disabled, obviously, blocks it. > >>> +#ifdef CONFIG_X86_64 >>> +EXPORT_SYMBOL_GPL(init_level4_pgt); >>> +#else >>> +EXPORT_SYMBOL_GPL(swapper_pg_dir); >>> +#endif >> >> like these really have no business in any module > > Well, that's why I took me 2 years to send this patch. Those symbols > shouldn't be used outside of page table debugging, so it didn't really > seem upstreamable. However, now that I need to do regular examination > of the page tables, I wanted to do it without the hacky thing above. I > want to do at will on our test images (we use the same kernel for > production and test, but production images leave out the test modules, > etc).
the code is small... how about making it a command line option to enable?
rather than making something like this a module
| |