Date: Mon, 24 Sep 2018 14:29:54 -0700 From: Kees Cook <keescook@...omium.org> To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <willy@...radead.org> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "daniel@...earbox.net" <daniel@...earbox.net>, "arjan@...ux.intel.com" <arjan@...ux.intel.com>, "jannh@...gle.com" <jannh@...gle.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "tglx@...utronix.de" <tglx@...utronix.de>, "kristen@...ux.intel.com" <kristen@...ux.intel.com>, "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>, "mingo@...hat.com" <mingo@...hat.com>, "alexei.starovoitov@...il.com" <alexei.starovoitov@...il.com>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, "Hansen, Dave" <dave.hansen@...el.com> Subject: Re: [PATCH v6 2/4] x86/modules: Increase randomization for modules On Mon, Sep 24, 2018 at 2:27 PM, Edgecombe, Rick P <rick.p.edgecombe@...el.com> wrote: > On Mon, 2018-09-24 at 12:58 -0700, Kees Cook wrote: >> On Mon, Sep 24, 2018 at 11:57 AM, Edgecombe, Rick P >> <rick.p.edgecombe@...el.com> wrote: >> > > Instead of having two open-coded __vmalloc_node_range() calls left in >> > > this after the change, can this be done in terms of a call to >> > > try_module_alloc() instead? I see they're slightly different, but it >> > > might be nice for making the two paths share more code. >> > Not sure what you mean. Across the whole change, there is one call >> > to __vmalloc_node_range, and one to __vmalloc_node_try_addr. >> I guess I meant the vmalloc calls -- one for node_range and one for >> node_try_addr. I was wondering if the logic could be combined in some >> way so that the __vmalloc_node_range() could be made in terms of the >> the helper that try_module_randomize_each() uses. But this could just >> be me hoping for nice-to-read changes. ;) >> >> -Kees > One thing I had been considering was to move the whole "try random locations, > then use backup" logic to vmalloc.c, and just have parameters for random area > size, number of tries, etc. This way it could be possibly be re-used for other > architectures for modules. Also on our list is to look at randomizing vmalloc > space (especially stacks), which may or may not involve using a similar method. > > So maybe bit pre-mature refactoring, but would also clean up the code in > module.c. Do you think it would be worth it? I'd love to hear thoughts from -mm folks. Andrew, Matthew? -Kees -- Kees Cook Pixel Security
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