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Date: Tue, 21 Mar 2017 13:40:43 -0700 From: Kees Cook <keescook@...omium.org> To: Evgenii Shatokhin <eugene.shatokhin@...dex.ru> Cc: "H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org> Subject: Re: 32-bit x86 system reboots automatically on resume from hibernate (ASLR issue?) On Tue, Mar 21, 2017 at 6:54 AM, Evgenii Shatokhin <eugene.shatokhin@...dex.ru> 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 <keescook@...omium.org> > 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? > Hardware: https://linux-hardware.org/index.php?probe=e6a06c64c7 > Config used to build the kernel at rev. 65fe935: > http://pastebin.com/AxEA6ahb > > If I understand it correctly, this commit just enabled ASLR by default > regardless of whether hibernation support was present or not. Before this > commit, ASLR was disabled on that system because hibernation was supported. > > To check if ASLR is really involved here, I rebuilt the kernel with > CONFIG_RANDOMIZE_BASE unset - now the system resumes OK from hibernation, no > auto reboots, no other visible problems so far. > > The problem does not show up in a 64-bit Linux system installed on the same > machine. Only the 32-bit system is affected. (Why would you want to run 32-bit kernels on a 64-bit system?) -Kees -- Kees Cook Pixel Security
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