libnvdimm: KASAN: global-out-of-bounds Read in internal_create_group

Because the last member of the "nvdimm_firmware_attributes" array
was not assigned a null ptr, when traversal of "grp->attrs" array
is out of bounds in "create_files" func.

func:
	create_files:
		->for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++)
			->....

BUG: KASAN: global-out-of-bounds in create_files fs/sysfs/group.c:43 [inline]
BUG: KASAN: global-out-of-bounds in internal_create_group+0x9d8/0xb20
fs/sysfs/group.c:149
Read of size 8 at addr ffffffff8a2e4cf0 by task kworker/u17:10/959

CPU: 2 PID: 959 Comm: kworker/u17:10 Not tainted 5.8.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Workqueue: events_unbound async_run_entry_fn
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0x5/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 create_files fs/sysfs/group.c:43 [inline]
 internal_create_group+0x9d8/0xb20 fs/sysfs/group.c:149
 internal_create_groups.part.0+0x90/0x140 fs/sysfs/group.c:189
 internal_create_groups fs/sysfs/group.c:185 [inline]
 sysfs_create_groups+0x25/0x50 fs/sysfs/group.c:215
 device_add_groups drivers/base/core.c:2024 [inline]
 device_add_attrs drivers/base/core.c:2178 [inline]
 device_add+0x7fd/0x1c40 drivers/base/core.c:2881
 nd_async_device_register+0x12/0x80 drivers/nvdimm/bus.c:506
 async_run_entry_fn+0x121/0x530 kernel/async.c:123
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the variable:
 nvdimm_firmware_attributes+0x10/0x40

Link: https://lore.kernel.org/r/20200812085501.30963-1-qiang.zhang@windriver.com
Link: https://lore.kernel.org/r/20200814150509.225615-1-vaibhav@linux.ibm.com
Fixes: 48001ea5 ("PM, libnvdimm: Add runtime firmware activation support")
Reported-by: syzbot+1cf0ffe61aecf46f588f@syzkaller.appspotmail.com
Reported-by: Sandipan Das <sandipan@linux.ibm.com>
Reported-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

drivers/nvdimm/dimm_devs.c

@@ -529,6 +529,7 @@ static DEVICE_ATTR_ADMIN_RW(activate);
 static struct attribute *nvdimm_firmware_attributes[] = {
 	&dev_attr_activate.attr,
 	&dev_attr_result.attr,
+	NULL,
 };
 
 static umode_t nvdimm_firmware_visible(struct kobject *kobj, struct attribute *a, int n)