Patch "cpuidle: check dev before usage in cpuidle_use_deepest_state()" has been added to the 4.11-stable tree

[<gregkh@linuxfoundation.org>]

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

    cpuidle: check dev before usage in cpuidle_use_deepest_state()

to the 4.11-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:
     cpuidle-check-dev-before-usage-in-cpuidle_use_deepest_state.patch
and it can be found in the queue-4.11 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 41dc750ea67f317c0deedde713d1728425524ef2 Mon Sep 17 00:00:00 2001
From: "Li, Fei" <fei.li@intel.com>
Date: Thu, 27 Apr 2017 01:47:25 +0000
Subject: cpuidle: check dev before usage in cpuidle_use_deepest_state()

From: Li, Fei <fei.li@intel.com>

commit 41dc750ea67f317c0deedde713d1728425524ef2 upstream.

In case of there is no cpuidle devices registered, dev will be null, and
panic will be triggered like below;
In this patch, add checking of dev before usage, like that done in
cpuidle_idle_call.

Panic without fix:
[  184.961328] BUG: unable to handle kernel NULL pointer dereference at
  (null)
[  184.961328] IP: cpuidle_use_deepest_state+0x30/0x60
...
[  184.961328]  play_idle+0x8d/0x210
[  184.961328]  ? __schedule+0x359/0x8e0
[  184.961328]  ? _raw_spin_unlock_irqrestore+0x28/0x50
[  184.961328]  ? kthread_queue_delayed_work+0x41/0x80
[  184.961328]  clamp_idle_injection_func+0x64/0x1e0

Fixes: bb8313b603eb8 (cpuidle: Allow enforcing deepest idle state selection)
Signed-off-by: Li, Fei <fei.li@intel.com>
Tested-by: Shi, Feng <fengx.shi@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/cpuidle/cpuidle.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -111,7 +111,8 @@ void cpuidle_use_deepest_state(bool enab
 
 	preempt_disable();
 	dev = cpuidle_get_device();
-	dev->use_deepest_state = enable;
+	if (dev)
+		dev->use_deepest_state = enable;
 	preempt_enable();
 }
 


Patches currently in stable-queue which might be from fei.li@intel.com are

queue-4.11/cpuidle-check-dev-before-usage-in-cpuidle_use_deepest_state.patch