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

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>

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 0ee1df0..61761aa 100644 (file)
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -300,12 +300,12 @@ static int create_image(int platform_mode)
        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;