From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 3CD3C6B03BC for ; Thu, 30 Mar 2017 13:20:37 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id a7so36872141pgn.1 for ; Thu, 30 Mar 2017 10:20:37 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id q188si2663197pfb.323.2017.03.30.10.20.35 for ; Thu, 30 Mar 2017 10:20:36 -0700 (PDT) Date: Thu, 30 Mar 2017 18:20:12 +0100 From: Mark Rutland Subject: Re: sudo x86info -a => kernel BUG at mm/usercopy.c:78! Message-ID: <20170330171701.GA8062@leverpostej> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Kees Cook Cc: Tommi Rantala , Linux-MM , LKML , Laura Abbott , Ingo Molnar , Josh Poimboeuf , Eric Biggers , Dave Jones On Thu, Mar 30, 2017 at 09:45:26AM -0700, 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? Presumably this is /dev/mem, with read_mem in drivers/char/mem.c. I guess you may have locked that down on your system anyhow. ;) Thanks, Mark. -- 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