Re: [PATCH v4 01/10] platform/x86/intel/pmt: fix a crashlog NULL pointer access

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Tue, 10 Jun 2025, Michael J. Ruhl wrote:

> Usage of the intel_pmt_read() for binary sysfs, requires a pcidev.  The
> current use of the endpoint value is only valid for telemetry endpoint
> usage.
> 
> Without the ep, the crashlog usage causes the following NULL pointer
> exception:
> 
> BUG: kernel NULL pointer dereference, address: 0000000000000000
> Oops: Oops: 0000 [#1] SMP NOPTI
> RIP: 0010:intel_pmt_read+0x3b/0x70 [pmt_class]
> Code:
> Call Trace:
>  <TASK>
>  ? sysfs_kf_bin_read+0xc0/0xe0
>  kernfs_fop_read_iter+0xac/0x1a0
>  vfs_read+0x26d/0x350
>  ksys_read+0x6b/0xe0
>  __x64_sys_read+0x1d/0x30
>  x64_sys_call+0x1bc8/0x1d70
>  do_syscall_64+0x6d/0x110
> 
> Augment the inte_pmt_entry to include the pcidev to allow for access to

intel_pmt_entry

> the pcidev and avoid the NULL pointer exception.
> 
> Fixes: 416eeb2e1fc7 ("platform/x86/intel/pmt: telemetry: Export API to read telemetry")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
> ---
>  drivers/platform/x86/intel/pmt/class.c | 3 ++-
>  drivers/platform/x86/intel/pmt/class.h | 1 +
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/intel/pmt/class.c b/drivers/platform/x86/intel/pmt/class.c
> index 7233b654bbad..d046e8752173 100644
> --- a/drivers/platform/x86/intel/pmt/class.c
> +++ b/drivers/platform/x86/intel/pmt/class.c
> @@ -97,7 +97,7 @@ intel_pmt_read(struct file *filp, struct kobject *kobj,
>  	if (count > entry->size - off)
>  		count = entry->size - off;
>  
> -	count = pmt_telem_read_mmio(entry->ep->pcidev, entry->cb, entry->header.guid, buf,
> +	count = pmt_telem_read_mmio(entry->pcidev, entry->cb, entry->header.guid, buf,
>  				    entry->base, off, count);
>  
>  	return count;
> @@ -252,6 +252,7 @@ static int intel_pmt_populate_entry(struct intel_pmt_entry *entry,
>  		return -EINVAL;
>  	}
>  
> +	entry->pcidev = pci_dev;
>  	entry->guid = header->guid;
>  	entry->size = header->size;
>  	entry->cb = ivdev->priv_data;
> diff --git a/drivers/platform/x86/intel/pmt/class.h b/drivers/platform/x86/intel/pmt/class.h
> index b2006d57779d..f6ce80c4e051 100644
> --- a/drivers/platform/x86/intel/pmt/class.h
> +++ b/drivers/platform/x86/intel/pmt/class.h
> @@ -39,6 +39,7 @@ struct intel_pmt_header {
>  
>  struct intel_pmt_entry {
>  	struct telem_endpoint	*ep;
> +	struct pci_dev		*pcidev;
>  	struct intel_pmt_header	header;
>  	struct bin_attribute	pmt_bin_attr;
>  	struct kobject		*kobj;
> 

-- 
 i.