From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id 711026B0397 for ; Thu, 30 Mar 2017 13:44:22 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id f191so18930545qka.7 for ; Thu, 30 Mar 2017 10:44:22 -0700 (PDT) Received: from mail-qk0-f177.google.com (mail-qk0-f177.google.com. [209.85.220.177]) by mx.google.com with ESMTPS id d25si2392555qtd.88.2017.03.30.10.44.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 Mar 2017 10:44:21 -0700 (PDT) Received: by mail-qk0-f177.google.com with SMTP id p22so46603401qka.3 for ; Thu, 30 Mar 2017 10:44:21 -0700 (PDT) Subject: Re: sudo x86info -a => kernel BUG at mm/usercopy.c:78! References: <3890813c-c891-89a5-c16f-66240a794319@redhat.com> From: Laura Abbott Message-ID: Date: Thu, 30 Mar 2017 10:44:18 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Kees Cook Cc: Tommi Rantala , Linux-MM , LKML , Ingo Molnar , Josh Poimboeuf , Mark Rutland , Eric Biggers , Dave Jones 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org