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

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 <[email protected]> know about it.

From: Dan Williams <[email protected]>
Date: Wed, 10 Aug 2016 15:59:09 -0700
Subject: tools/testing/nvdimm: fix SIGTERM vs hotplug crash

From: Dan Williams <[email protected]>

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

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

@@ -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 [email protected] are

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