Re: [PATCH v2 2/4] ACPI: NFIT: core: Fix acpi_nfit_init() error cleanup

[Dave Jiang <dave.jiang@intel.com>]

On 6/3/26 10:57 AM, Rafael J. Wysocki wrote:
> From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> 
> If acpi_nfit_init() fails after adding the acpi_desc object to the
> acpi_descs list, that object is never removed from that list because
> the acpi_nfit_shutdown() devm action is not added for the NFIT device
> in that case.  Next, the acpi_nfit_init() failure causes
> acpi_nfit_probe() to fail, the acpi_desc object is freed, and a
> dangling pointer is left behind in the acpi_descs.  Any subsequent
> ACPI Machine Check Exception will trigger nfit_handle_mce() which
> iterates over acpi_descs and so a use-after-free will occur.
> 
> Moreover, if acpi_nfit_probe() returns 0 after installing a notify
> handler for the NFIT device and without allocating the acpi_desc
> object and setting the NFIT device's driver data pointer, the
> acpi_desc object will be allocated by acpi_nfit_update_notify()
> and acpi_nfit_init() will be called to initialize it.  Regardless
> of whether or not acpi_nfit_init() fails in that case, the
> acpi_nfit_shutdown() devm action is not added for the NFIT device
> and acpi_desc is never removed from the acpi_descs list.  If the
> acpi_desc object is freed subsequently on driver removal, any
> subsequent ACPI MCE will lead to a use-after-free like in the
> previous case.
> 
> To address the first issue mentioned above, make acpi_nfit_probe()
> call acpi_nfit_shutdown() directly on acpi_nfit_init() failures and
> to address the other one, add a remove callback to the driver and
> make it call acpi_nfit_shutdown().  Also, since it is now possible to
> pass NULL to acpi_nfit_shutdown() or the acpi_desc object passed to it
> may not have been initialized, add checks against NULL for acpi_desc and
> its nvdimm_bus field to that function and make acpi_nfit_unregister()
> clear the latter after unregistering the NVDIMM bus.
> 
> Fixes: a61fe6f7902e ("nfit, tools/testing/nvdimm: unify common init for acpi_nfit_desc")
> Fixes: fbabd829fe76 ("acpi, nfit: fix module unload vs workqueue shutdown race")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: All applicable <stable@vger.kernel.org>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>


> ---
>  drivers/acpi/nfit/core.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index 8024cd3cad14..01c73be0bd00 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -3069,6 +3069,8 @@ static void acpi_nfit_unregister(void *data)
>  	struct acpi_nfit_desc *acpi_desc = data;
>  
>  	nvdimm_bus_unregister(acpi_desc->nvdimm_bus);
> +	/* The nvdimm_bus object may have been freed, so clear the pointer. */
> +	acpi_desc->nvdimm_bus = NULL;
>  }
>  
>  int acpi_nfit_init(struct acpi_nfit_desc *acpi_desc, void *data, acpi_size sz)
> @@ -3301,7 +3303,10 @@ static void acpi_nfit_notify(acpi_handle handle, u32 event, void *data)
>  void acpi_nfit_shutdown(void *data)
>  {
>  	struct acpi_nfit_desc *acpi_desc = data;
> -	struct device *bus_dev = to_nvdimm_bus_dev(acpi_desc->nvdimm_bus);
> +	struct device *bus_dev;
> +
> +	if (!acpi_desc || !acpi_desc->nvdimm_bus)
> +		return;
>  
>  	/*
>  	 * Destruct under acpi_desc_lock so that nfit_handle_mce does not
> @@ -3316,6 +3321,7 @@ void acpi_nfit_shutdown(void *data)
>  	mutex_unlock(&acpi_desc->init_mutex);
>  	cancel_delayed_work_sync(&acpi_desc->dwork);
>  
> +	bus_dev = to_nvdimm_bus_dev(acpi_desc->nvdimm_bus);
>  	/*
>  	 * Bounce the nvdimm bus lock to make sure any in-flight
>  	 * acpi_nfit_ars_rescan() submissions have had a chance to
> @@ -3388,9 +3394,14 @@ static int acpi_nfit_probe(struct platform_device *pdev)
>  				sz - sizeof(struct acpi_table_nfit));
>  
>  	if (rc)
> -		return rc;
> +		acpi_nfit_shutdown(acpi_desc);
>  
> -	return devm_add_action_or_reset(dev, acpi_nfit_shutdown, acpi_desc);
> +	return rc;
> +}
> +
> +static void acpi_nfit_remove(struct platform_device *pdev)
> +{
> +	acpi_nfit_shutdown(platform_get_drvdata(pdev));
>  }
>  
>  static void acpi_nfit_update_notify(struct device *dev, acpi_handle handle)
> @@ -3474,6 +3485,7 @@ MODULE_DEVICE_TABLE(acpi, acpi_nfit_ids);
>  
>  static struct platform_driver acpi_nfit_driver = {
>  	.probe = acpi_nfit_probe,
> +	.remove = acpi_nfit_remove,
>  	.driver = {
>  		.name = "acpi-nfit",
>  		.acpi_match_table = acpi_nfit_ids,