From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] Xen PV domain regression with KASLR enabled (kernel 3.16) Date: Fri, 8 Aug 2014 13:43:01 +0100 Message-ID: <53E4C5D5.2090103@citrix.com> References: <53E4B281.5050302@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53E4B281.5050302@canonical.com> Sender: linux-kernel-owner@vger.kernel.org To: Stefan Bader , "xen-devel@lists.xensource.com" , Linux Kernel Mailing List Cc: Kees Cook , David Vrabel List-Id: xen-devel@lists.xenproject.org On 08/08/14 12:20, Stefan Bader wrote: > Unfortunately I have not yet figured out why this happens, but can confirm by > compiling with or without CONFIG_RANDOMIZE_BASE being set that without KASLR all > is ok, but with it enabled there are issues (actually a dom0 does not even boot > as a follow up error). > > Details can be seen in [1] but basically this is always some portion of a > vmalloc allocation failing after hitting a freshly allocated PTE space not being > PTE_NONE (usually from a module load triggered by systemd-udevd). In the > non-dom0 case this repeats many times but ends in a guest that allows login. In > the dom0 case there is a more fatal error at some point causing a crash. > > I have not tried this for a normal PV guest but for dom0 it also does not help > to add "nokaslr" to the kernel command-line. Maybe it's overlapping with regions of the virtual address space reserved for Xen? What the the VA that fails? David