Date: Mon, 09 Nov 2015 11:02:47 +0100 From: Rasmus Villemoes <linux@...musvillemoes.dk> To: kernel-hardening@...ts.openwall.com Subject: Re: Kernel Self Protection Project On Sat, Nov 07 2015, Quentin Casasnovas <quentin.casasnovas@...cle.com> wrote: > On 2015-11-06, Kees Cook <keescook@...omium.org> wrote: >> On Fri, Nov 6, 2015 at 8:00 AM, Quentin Casasnovas >><quentin.casasnovas@...cle.com> wrote: >>>> >>>> For now, I'm going to focus on taking a look at the PAX_SIZE_OVERFLOW >>>> gcc plugin, which will also get us the gcc plugin infrastructure. >>>> Other people, please speak up on what you'd like to tackle. >>>> >>> >>> Not that it's complex but I already have a branch with the gcc plugin >>> infrastructure split up if you're interested and you reckon that can save >>> you some time. >> >> Sure, what's the URL? >> > > I've pushed the three of them onto: > > https://github.com/casasnovas/linux/commits/quentin-spk-gcc-plugin > > It lacks Documentation for now, but you can have a look at the branch > quentin-fuzz-gccplugin which adds an instrumentation plugin (converted from > the gcc patch Dmitry Vyukov wrote for syzkaller). > > Adding a plugin should be simple, add its name to $(HOSTLIBS)-y, and use > the regular kbuild system way to specify from which source files it is > built, CFLAGS, etc. > > $(HOSTLIBS)-y = foo.so > foo-objs = foo.c bar.c > > And then to have some compilations units be compiled using foo.so, they > just need the following in their CFLAGS: > > -fplugin=$(objtree)/path/to/foo.so Nice, thanks. But wouldn't it be even more userfriendly to have these things driven by Kconfig? So let (use of) each plugin depend on a CONFIG_GCCPLUGIN_XYZ variable, which will automatically turn itself off (with a warning) if that plugin can't be used for whatever reason. That'll also give a natural place to say a little about the plugin (though I also think Documentation/gccplugins/* should be created). We could hide these behind CONFIG_USE_GCCPLUGINS to make it easy for people to turn off. I suppose some plugins are really all-or-nothing (e.g. when randomizing structs, the various TUs better agree on what shuffling has been done), so for them it doesn't make sense to apply to individual C files. Is something done to ensure that, and if not, can it be done with some linker magic? (Something like putting a hash of the used random seed in each object file and make the linker complain if there are distinct definitions of that magic symbol.) Rasmus
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