Patch "tools/testing/nvdimm: fix SIGTERM vs hotplug crash" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    tools/testing/nvdimm: fix SIGTERM vs hotplug crash

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:
     tools-testing-nvdimm-fix-sigterm-vs-hotplug-crash.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 d8d378fa1a0c98ecb50ca52c9bf3bc14e25aa2d2 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Wed, 10 Aug 2016 15:59:09 -0700
Subject: tools/testing/nvdimm: fix SIGTERM vs hotplug crash

From: Dan Williams <dan.j.williams@intel.com>

commit d8d378fa1a0c98ecb50ca52c9bf3bc14e25aa2d2 upstream.

The unit tests crash when hotplug races the previous probe. This race
requires that the loading of the nfit_test module be terminated with
SIGTERM, and the module to be unloaded while the ars scan is still
running.

In contrast to the normal nfit driver, the unit test calls
acpi_nfit_init() twice to simulate hotplug, whereas the nominal case
goes through the acpi_nfit_notify() event handler.  The
acpi_nfit_notify() path is careful to flush the previous region
registration before servicing the hotplug event. The unit test was
missing this guarantee.

 BUG: unable to handle kernel NULL pointer dereference at           (null)
 IP: [<ffffffff810cdce7>] pwq_activate_delayed_work+0x47/0x170
 [..]
 Call Trace:
  [<ffffffff810ce186>] pwq_dec_nr_in_flight+0x66/0xa0
  [<ffffffff810ce490>] process_one_work+0x2d0/0x680
  [<ffffffff810ce331>] ? process_one_work+0x171/0x680
  [<ffffffff810ce88e>] worker_thread+0x4e/0x480
  [<ffffffff810ce840>] ? process_one_work+0x680/0x680
  [<ffffffff810ce840>] ? process_one_work+0x680/0x680
  [<ffffffff810d5343>] kthread+0xf3/0x110
  [<ffffffff8199846f>] ret_from_fork+0x1f/0x40
  [<ffffffff810d5250>] ? kthread_create_on_node+0x230/0x230

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 tools/testing/nvdimm/test/nfit.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/tools/testing/nvdimm/test/nfit.c
+++ b/tools/testing/nvdimm/test/nfit.c
@@ -13,6 +13,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 #include <linux/platform_device.h>
 #include <linux/dma-mapping.h>
+#include <linux/workqueue.h>
 #include <linux/libnvdimm.h>
 #include <linux/vmalloc.h>
 #include <linux/device.h>
@@ -1246,6 +1247,7 @@ static int nfit_test_probe(struct platfo
 	if (nfit_test->setup != nfit_test0_setup)
 		return 0;
 
+	flush_work(&acpi_desc->work);
 	nfit_test->setup_hotplug = 1;
 	nfit_test->setup(nfit_test);
 


Patches currently in stable-queue which might be from dan.j.williams@intel.com are

queue-4.4/tools-testing-nvdimm-fix-sigterm-vs-hotplug-crash.patch