Re: [PATCH 3/3] platform/x86/intel/tpmi/plr: Prevent fault during unbind

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

On Wed, 29 Apr 2026, Srinivas Pandruvada wrote:

> This driver faults when intel vsec driver unbound from PCI driver
> interface. For example:
> 
> echo 0000:00:03.1 > /sys/bus/pci/drivers/intel_vsec/unbind
> 
> This is caused by accessing plr->dbgfs_dir after vsec_tpmi driver is
> removed. Here vsec_tpmi driver is the parent. On unbind, the parent
> device remove callback is called first which here will remove debugfs
> interface. Hence plr->dbgfs_dir is no longer valid.
> 
> Register notifier for TPMI_CORE_EXIT and make this pointer to NULL,
> so that debugfs_remove_recursive() is not called with bad plr->dbgfs_dir
> pointer.
> 
> After notifier is returned the vsec_tpmi driver will call remove debugfs
> by calling debugfs_remove_recursive().
> 
> Fixes: 811f67c51636 ("platform/x86/intel/tpmi: Add new auxiliary driver for performance limits")
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> Cc: <Stable@vger.kernel.org>
> ---
>  drivers/platform/x86/intel/plr_tpmi.c | 43 +++++++++++++++++++++++++--
>  1 file changed, 41 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel/plr_tpmi.c b/drivers/platform/x86/intel/plr_tpmi.c
> index 05727169f49c..644df673896b 100644
> --- a/drivers/platform/x86/intel/plr_tpmi.c
> +++ b/drivers/platform/x86/intel/plr_tpmi.c
> @@ -22,6 +22,7 @@
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/mutex.h>
> +#include <linux/notifier.h>
>  #include <linux/seq_file.h>
>  #include <linux/sprintf.h>
>  #include <linux/types.h>
> @@ -60,6 +61,8 @@ struct tpmi_plr {
>  	struct tpmi_plr_die *die_info;
>  	int num_dies;
>  	struct auxiliary_device *auxdev;
> +	struct notifier_block nb;
> +	struct mutex lock; /* Protect access to dbgfs_dir  */

Extra whitespace.

Move the comment slightly more right as there's place.

>  };
>  
>  static const char * const plr_coarse_reasons[] = {
> @@ -255,6 +258,30 @@ static ssize_t plr_status_write(struct file *filp, const char __user *ubuf,
>  }
>  DEFINE_SHOW_STORE_ATTRIBUTE(plr_status);
>  
> +static int intel_plr_notify(struct notifier_block *self, unsigned long action, void *data)
> +{
> +	struct tpmi_plr *plr = container_of(self, struct tpmi_plr, nb);
> +
> +	if (action == TPMI_CORE_EXIT) {
> +		guard(mutex)(&plr->lock);
> +		plr->dbgfs_dir = NULL;
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static int intel_plr_register_notifier(struct notifier_block *nb)
> +{
> +	nb->notifier_call = intel_plr_notify;
> +	nb->priority = 0;
> +	return tpmi_register_notifier(nb);
> +}
> +
> +static void intel_plr_unregister_notifier(struct notifier_block *nb)
> +{
> +	tpmi_unregister_notifier(nb);
> +}
> +
>  static int intel_plr_probe(struct auxiliary_device *auxdev, const struct auxiliary_device_id *id)
>  {
>  	struct oobmsm_plat_info *plat_info;
> @@ -282,10 +309,16 @@ static int intel_plr_probe(struct auxiliary_device *auxdev, const struct auxilia
>  	if (!plr)
>  		return -ENOMEM;
>  
> +	mutex_init(&plr->lock);

This lacks pairing destroy, but you can probably use devm_mutex_init() as 
there's devm_*() below.

> +
> +	intel_plr_register_notifier(&plr->nb);
> +
>  	plr->die_info = devm_kcalloc(&auxdev->dev, num_resources, sizeof(*plr->die_info),
>  				     GFP_KERNEL);
> -	if (!plr->die_info)
> -		return -ENOMEM;
> +	if (!plr->die_info) {
> +		err = -ENOMEM;
> +		goto err_notify;
> +	}
>  
>  	plr->num_dies = num_resources;
>  	plr->dbgfs_dir = debugfs_create_dir("plr", dentry);
> @@ -326,6 +359,9 @@ static int intel_plr_probe(struct auxiliary_device *auxdev, const struct auxilia
>  
>  err:
>  	debugfs_remove_recursive(plr->dbgfs_dir);
> +err_notify:
> +	intel_plr_unregister_notifier(&plr->nb);
> +
>  	return err;
>  }
>  
> @@ -333,6 +369,9 @@ static void intel_plr_remove(struct auxiliary_device *auxdev)
>  {
>  	struct tpmi_plr *plr = auxiliary_get_drvdata(auxdev);
>  
> +	intel_plr_unregister_notifier(&plr->nb);
> +
> +	guard(mutex)(&plr->lock);
>  	debugfs_remove_recursive(plr->dbgfs_dir);
>  }
>  
> 

-- 
 i.