Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934165AbdC3RoY (ORCPT ); Thu, 30 Mar 2017 13:44:24 -0400 Received: from mail-qk0-f179.google.com ([209.85.220.179]:34161 "EHLO mail-qk0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933150AbdC3RoW (ORCPT ); Thu, 30 Mar 2017 13:44:22 -0400 Subject: Re: sudo x86info -a => kernel BUG at mm/usercopy.c:78! To: Kees Cook References: <3890813c-c891-89a5-c16f-66240a794319@redhat.com> Cc: Tommi Rantala , Linux-MM , LKML , Ingo Molnar , Josh Poimboeuf , Mark Rutland , Eric Biggers , Dave Jones From: Laura Abbott Message-ID: Date: Thu, 30 Mar 2017 10:44:18 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2010 Lines: 58 On 03/30/2017 10:37 AM, Kees Cook wrote: > On Thu, Mar 30, 2017 at 10:27 AM, Laura Abbott wrote: >> On 03/30/2017 09:45 AM, Kees Cook wrote: >>> On Wed, Mar 29, 2017 at 11:44 PM, Tommi Rantala >>> wrote: >>>> Hi, >>>> >>>> Running: >>>> >>>> $ sudo x86info -a >>>> >>>> On this HP ZBook 15 G3 laptop kills the x86info process with segfault and >>>> produces the following kernel BUG. >>>> >>>> $ git describe >>>> v4.11-rc4-40-gfe82203 >>>> >>>> It is also reproducible with the fedora kernel: 4.9.14-200.fc25.x86_64 >>>> >>>> Full dmesg output here: https://pastebin.com/raw/Kur2mpZq >>>> >>>> [ 51.418954] usercopy: kernel memory exposure attempt detected from >>>> ffff880000090000 (dma-kmalloc-256) (4096 bytes) >>> >>> This seems like a real exposure: the copy is attempting to read 4096 >>> bytes from a 256 byte object. >>> >>>> [...] >>>> [ 51.419063] Call Trace: >>>> [ 51.419066] read_mem+0x70/0x120 >>>> [ 51.419069] __vfs_read+0x28/0x130 >>>> [ 51.419072] ? security_file_permission+0x9b/0xb0 >>>> [ 51.419075] ? rw_verify_area+0x4e/0xb0 >>>> [ 51.419077] vfs_read+0x96/0x130 >>>> [ 51.419079] SyS_read+0x46/0xb0 >>>> [ 51.419082] ? SyS_lseek+0x87/0xb0 >>>> [ 51.419085] entry_SYSCALL_64_fastpath+0x1a/0xa9 >>> >>> I can't reproduce this myself, so I assume it's some specific /proc or >>> /sys file that I don't have. Are you able to get a strace of x86info >>> as it runs to see which file it is attempting to read here? >> >> I can't see this on any of my Fedora systems. It looks like this >> is trying to read /dev/mem so I suspect your BIOS is putting out >> unexpected values. If you turn off hardened usercopy does x86info >> give you reasonable values? I'd also echo getting an strace. > > Reads out of /dev/mem should be restricted to non-RAM on Fedora, yes? > > Tommi, do your kernels have CONFIG_STRICT_DEVMEM=y ? > > -Kees > CONFIG_STRICT_DEVMEM should be on in all Fedora kernels. Thanks, Laura