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

[Ira Weiny <ira.weiny@intel.com>]

On Fri, Aug 14, 2020 at 08:35:09PM +0530, Vaibhav Jain wrote:
> 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@linux.ibm.com>
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>

Reviewed-by: Ira Weiny <ira.weiny@intel.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
>