Patch "PM / hibernate: Restore processor state before using per-CPU variables" has been added to the 4.4-stable tree

Patch "PM / hibernate: Restore processor state before using per-CPU variables" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    PM / hibernate: Restore processor state before using per-CPU variables

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     pm-hibernate-restore-processor-state-before-using-per-cpu-variables.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 62822e2ec4ad091ba31f823f577ef80db52e3c2c Mon Sep 17 00:00:00 2001
From: Thomas Garnier <thgarnie@google.com>
Date: Thu, 11 Aug 2016 14:49:29 -0700
Subject: PM / hibernate: Restore processor state before using per-CPU variables

From: Thomas Garnier <thgarnie@google.com>

commit 62822e2ec4ad091ba31f823f577ef80db52e3c2c upstream.

Restore the processor state before calling any other functions to
ensure per-CPU variables can be used with KASLR memory randomization.

Tracing functions use per-CPU variables (GS based on x86) and one was
called just before restoring the processor state fully. It resulted
in a double fault when both the tracing & the exception handler
functions tried to use a per-CPU variable.

Fixes: bb3632c6101b (PM / sleep: trace events for suspend/resume)
Reported-and-tested-by: Borislav Petkov <bp@suse.de>
Reported-by: Jiri Kosina <jikos@kernel.org>
Tested-by: Rafael J. Wysocki <rafael@kernel.org>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Garnier <thgarnie@google.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/power/hibernate.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -299,12 +299,12 @@ static int create_image(int platform_mod
 	save_processor_state();
 	trace_suspend_resume(TPS("machine_suspend"), PM_EVENT_HIBERNATE, true);
 	error = swsusp_arch_suspend();
+	/* Restore control flow magically appears here */
+	restore_processor_state();
 	trace_suspend_resume(TPS("machine_suspend"), PM_EVENT_HIBERNATE, false);
 	if (error)
 		printk(KERN_ERR "PM: Error %d creating hibernation image\n",
 			error);
-	/* Restore control flow magically appears here */
-	restore_processor_state();
 	if (!in_suspend)
 		events_check_enabled = false;
 


Patches currently in stable-queue which might be from thgarnie@google.com are

queue-4.4/pm-hibernate-restore-processor-state-before-using-per-cpu-variables.patch