Date: Thu, 14 Apr 2016 23:06:41 +0800 From: Baoquan He <bhe@...hat.com> To: Kees Cook <keescook@...omium.org> Cc: Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...hat.com>, LKML <linux-kernel@...r.kernel.org>, Yinghai Lu <yinghai@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>, Vivek Goyal <vgoyal@...hat.com>, Andy Lutomirski <luto@...nel.org>, lasse.collin@...aani.org, Andrew Morton <akpm@...ux-foundation.org>, Dave Young <dyoung@...hat.com>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH v4 00/20] x86, boot: kaslr cleanup and 64bit kaslr support On 04/13/16 at 11:02pm, Kees Cook wrote: > On Wed, Apr 13, 2016 at 7:11 AM, Kees Cook <keescook@...omium.org> wrote: > > On Wed, Apr 13, 2016 at 3:19 AM, Ingo Molnar <mingo@...nel.org> wrote: > >> > >> * Kees Cook <keescook@...omium.org> wrote: > >> > >>> FWIW, I've also had this tree up in my git branches, and the 0day > >>> tester hasn't complained at all about it in the last two weeks. I'd > >>> really like to see this in -next to fix the >4G (mainly kexec) issues > >>> and get us to feature parity with the arm64 kASLR work (randomized > >>> virtual address). > > So, I've done this and suddenly realized I hadn't boot-tested i386. It > doesn't work, unfortunately. (Which I find strange: I'd expect 0day to > have noticed...) > > Baoquan, have you tested this on 32-bit systems? I get a variety of > failures. Either it boots okay, it reboots, or I get tons of pte > errors like this: Hi Kees, I am sorry I didn't notice the change impacts i386. I got a i386 machine and had tests. Found i386 can't take separate randomzation since there's difference between i386 and x86_64. x86_64 has phys_base and can translate virt addr and phys addr according to below formula: paddr = vaddr - __START_KERNEL_map + phys_base; However i386 can only do like this: paddr = vaddr - PAGE_OFFSET; Besides i386 has to reserve 128M for VMALLOC at the end of kernel virtual address. So for i386 area 768M is the upper limit for randomization. But I am fine with the KERNEL_IMAGE_SIZE, the old default value. What do you say about this? So the plan should be keeping the old style of randomization for i386 system: 1) Disable virtual address randomization in i386 case because it's useless. This should be done in patch: x86, KASLR: Randomize virtual address separately 2) Add an upper limit for physical randomization if it's i386 system. x86, KASLR: Add physical address randomization >4G I just got a test machine in office, and haven't had time to change code. You can change it directly, or I will do it tomorrow. Thanks > > [ 0.000000] clearing pte for ram above max_low_pfn: pfn: 37dcc pmd: > f9144f7c pmd phys: 39144f7c pte: f9a1b730 pte phys: 39a1b730 > > Can you confirm? I suspect relocation problems, but ran out of time > today to debug it. > > I have the entire series with cleaned up changelogs and various other > refactorings up here now: > > http://git.kernel.org/cgit/linux/kernel/git/kees/linux.git/log/?h=kaslr/highmem > > Thanks! > > -Kees > > -- > Kees Cook > Chrome OS & Brillo Security
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