From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f197.google.com (mail-qt0-f197.google.com [209.85.216.197]) by kanga.kvack.org (Postfix) with ESMTP id C54786B03C0 for ; Thu, 30 Mar 2017 13:27:52 -0400 (EDT) Received: by mail-qt0-f197.google.com with SMTP id n37so18478720qtb.7 for ; Thu, 30 Mar 2017 10:27:52 -0700 (PDT) Received: from mail-qk0-f174.google.com (mail-qk0-f174.google.com. [209.85.220.174]) by mx.google.com with ESMTPS id x33si2347453qta.126.2017.03.30.10.27.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 Mar 2017 10:27:51 -0700 (PDT) Received: by mail-qk0-f174.google.com with SMTP id d10so46401474qke.1 for ; Thu, 30 Mar 2017 10:27:51 -0700 (PDT) Subject: Re: sudo x86info -a => kernel BUG at mm/usercopy.c:78! References: From: Laura Abbott Message-ID: <3890813c-c891-89a5-c16f-66240a794319@redhat.com> Date: Thu, 30 Mar 2017 10:27:47 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Kees Cook , Tommi Rantala Cc: Linux-MM , LKML , Ingo Molnar , Josh Poimboeuf , Mark Rutland , Eric Biggers , Dave Jones 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? > > Thanks! > > -Kees > 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. 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