Date: Thu, 17 Nov 2016 11:56:50 -0800 From: Kees Cook <keescook@...omium.org> To: Michael Ellerman <mpe@...erman.id.au> Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: Re: [PATCH] lkdtm: Add tests for LIST_POISON and ZERO_SIZE_PTR On Thu, Nov 17, 2016 at 2:53 AM, Michael Ellerman <mpe@...erman.id.au> wrote: > kbuild test robot <lkp@...el.com> writes: >> [auto build test ERROR on char-misc/char-misc-testing] >> [also build test ERROR on v4.9-rc5] >> [cannot apply to next-20161115] >> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] >> >> url: https://github.com/0day-ci/linux/commits/Michael-Ellerman/lkdtm-Add-tests-for-LIST_POISON-and-ZERO_SIZE_PTR/20161115-235441 >> config: i386-randconfig-i0-201646 (attached as .config) >> compiler: gcc-4.8 (Debian 4.8.4-1) 4.8.4 >> reproduce: >> # save the attached .config to linux build tree >> make ARCH=i386 >> >> All errors (new ones prefixed by >>): >> >>>> ERROR: "mmap_min_addr" [drivers/misc/lkdtm.ko] undefined! > > I couldn't see what was causing this, but of course it's just that > mmap_min_addr is not exported, and in that config LKDTM is a module. > > I always build it in which is why I didn't notice. > > I'm not sure we want to EXPORT_SYMBOL mmap_min_addr just for this test > do we? I could change the test to use mmap_min_addr if LKDTM is > built-in, and otherwise just map at zero. Dunno. Because of lkdtm's moduleness, I've had to put a lot of weird stuff into EXPORT_SYMBOL_GPL(). mmap_min_addr is more sensitive than most, though. How about just hard-coding it as 64k instead of using mmap_min_addr? Anyone using >64k is likely going to understand why lkdtm failed. -Kees -- Kees Cook Nexus Security
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