On Wednesday, March 22, 2017 11:58:55 AM Kees Cook wrote: > On Wed, Mar 22, 2017 at 5:50 AM, Evgenii Shatokhin > <[email protected]> wrote: > > On 21.03.2017 23:40, Kees Cook wrote: > >> > >> On Tue, Mar 21, 2017 at 6:54 AM, Evgenii Shatokhin > >> <[email protected]> wrote: > >>> > >>> Hi, > >>> > >>> One of my x86 machines with a 32-bit Linux system (ROSA Linux in this > >>> case) > >>> automatically reboots when it tries to resume from hibernate. This > >>> happens > >>> shortly after "Image loading progress 100%" message is shown on the > >>> screen. > >>> > >>> No traces of the error are in the system log after reboot though. > >>> > >>> The problem is present at least in the mainline kernels 4.8 - 4.10. With > >>> earlier versions (I tried 4.4, 4.5, etc.), the system resumes OK. > >>> > >>> The bisection pointed to the following commit as the first "bad" one: > >>> > >>> commit 65fe935dd2387a4faf15314c73f5e6d31ef0217e > >>> Author: Kees Cook <[email protected]> > >>> Date: Mon Jun 13 15:10:02 2016 -0700 > >>> > >>> x86/KASLR, x86/power: Remove x86 hibernation restrictions > >> > >> > >> Hrm, perhaps the 32-bit hibernation code still isn't KASLR-safe. If > >> you boot with nokaslr on the kernel command line, does the problem go > >> away? > > > > > > Yes. The problem does not show up when I boot the system with 'nokaslr'. > > Okay, it looks like we need to either partially revert that commit > (i.e. make the by-default-prefer-hibernation logic only happen on > 32-bit x86), swap the logic (i.e. by-default-prefer-KASLR on 32-bit), > or make KASLR be blocked by hibernation in Kconfig (as it was a long > time ago). > > Rafael, do you have a preference here?
I'd say let's make KASLR and hibernation mutually exclusive on 32-bit and it really doesn't matter to me which one is preferred as long as it is clear that one will be disabled by the other (each way). And I don't see why 64-bit would need to be affected by this at all, frankly. I still have a patch from Pavel to improve things in 32-bit hibernation land, but it still requires some time and effort and I don't see volunteers for that work. Thanks, Rafael
