[PATCH] libnvdimm: Add a NULL entry to 'nvdimm_firmware_attributes'

[Vaibhav Jain]

We recently discovered a kernel oops with 'papr_scm' module while
booting ppc64 phyp guest with following back-trace:

BUG: Kernel NULL pointer dereference on write at 0x00000188
Faulting instruction address: 0xc0000000005d7084
Oops: Kernel access of bad area, sig: 11 [#1]
<snip>
Call Trace:
 internal_create_group+0x128/0x4c0 (unreliable)
 internal_create_groups.part.4+0x70/0x130
 device_add+0x458/0x9c0
 nd_async_device_register+0x28/0xa0 [libnvdimm]
 async_run_entry_fn+0x78/0x1f0
 process_one_work+0x2c0/0x5b0
 worker_thread+0x88/0x650
 kthread+0x1a8/0x1b0
 ret_from_kernel_thread+0x5c/0x6c

A bisect lead to the 'commit 48001ea50d17f ("PM, libnvdimm: Add runtime
firmware activation support")' and on investigation discovered that
the newly introduced 'struct attribute *nvdimm_firmware_attributes[]'
is missing a terminating NULL entry in the array. This causes a loop
in sysfs's 'create_files()' to read garbage beyond bounds of
'nvdimm_firmware_attributes' and trigger the oops.

Fixes: 48001ea50d17f ("PM, libnvdimm: Add runtime firmware activation support")
Reported-by: Sandipan Das <sandipan at linux.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
---
 drivers/nvdimm/dimm_devs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
index 61374def51555..b59032e0859b7 100644
--- a/drivers/nvdimm/dimm_devs.c
+++ b/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)
-- 
2.26.2