Re: [PATCH 3/3] platform/x86: thinkpad_acpi: use __free(kfree) for automatic cleanup

[Mark Pearson]

Thanks Dmitry,

On Thu, Aug 6, 2026, at 2:19 AM, Dmitry Torokhov wrote:
> Use __free(kfree) for local pointer allocations in dispatch_proc_write(),
> tpacpi_brightness_get_ecnvram(), and auxmac_init().
>
> This ensures automatic memory cleanup when exiting function scope and
> removes explicit kfree() calls on exit paths.
>
> Assisted-by: Antigravity:gemini-3.6-flash
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> ---
>  drivers/platform/x86/lenovo/thinkpad_acpi.c | 40 +++++++--------------
>  1 file changed, 13 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c 
> b/drivers/platform/x86/lenovo/thinkpad_acpi.c
> index 0d0d6fe7eecd..200e20f90a4b 100644
> --- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
> +++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
> @@ -885,7 +885,6 @@ static ssize_t dispatch_proc_write(struct file 
> *file,
>  			size_t count, loff_t *pos)
>  {
>  	struct ibm_struct *ibm = pde_data(file_inode(file));
> -	char *kernbuf;
>  	int ret;
> 
>  	if (!ibm || !ibm->write)
> @@ -893,16 +892,15 @@ static ssize_t dispatch_proc_write(struct file *file,
>  	if (count > PAGE_SIZE - 1)
>  		return -EINVAL;
> 
> -	kernbuf = memdup_user_nul(userbuf, count);
> +	char *kernbuf __free(kfree) = memdup_user_nul(userbuf, count);
>  	if (IS_ERR(kernbuf))
>  		return PTR_ERR(kernbuf);
> -	ret = ibm->write(kernbuf);
> -	if (ret == 0)
> -		ret = count;
> 
> -	kfree(kernbuf);
> +	ret = ibm->write(kernbuf);
> +	if (ret)
> +		return ret;
> 
> -	return ret;
> +	return count;
>  }
> 
>  static const struct proc_ops dispatch_proc_ops = {
> @@ -6628,26 +6626,21 @@ static const struct backlight_ops ibm_backlight_data = {
>  static int __init tpacpi_evaluate_bcl(struct acpi_device *adev, void *not_used)
>  {
>  	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> -	union acpi_object *obj;
>  	acpi_status status;
> -	int rc;
> 
>  	status = acpi_evaluate_object(adev->handle, "_BCL", NULL, &buffer);
>  	if (ACPI_FAILURE(status))
>  		return 0;
> 
> -	obj = buffer.pointer;
> +	union acpi_object *obj __free(kfree) = buffer.pointer;
>  	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
>  		acpi_handle_info(adev->handle,
>  				 "Unknown _BCL data, please report this to %s\n",
>  				 TPACPI_MAIL);
> -		rc = 0;
> -	} else {
> -		rc = obj->package.count;
> +		return 0;
>  	}
> -	kfree(obj);
> 
> -	return rc;
> +	return obj->package.count;
>  }
> 
>  /*
> @@ -10989,24 +10982,23 @@ static int auxmac_init(struct ibm_init_struct *iibm)
>  {
>  	acpi_status status;
>  	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> -	union acpi_object *obj;
> 
> -	status = acpi_evaluate_object(NULL, "\\MACA", NULL, &buffer);
> +	strscpy(auxmac, "unavailable", sizeof(auxmac));
> 
> +	status = acpi_evaluate_object(NULL, "\\MACA", NULL, &buffer);
>  	if (ACPI_FAILURE(status))
>  		return -ENODEV;
> 
> -	obj = buffer.pointer;
> -
> +	union acpi_object *obj __free(kfree) = buffer.pointer;
>  	if (obj->type != ACPI_TYPE_STRING || obj->string.length != AUXMAC_STRLEN) {
>  		pr_info("Invalid buffer for MAC address pass-through.\n");
> -		goto auxmacinvalid;
> +		return 0;
>  	}
> 
>  	if (obj->string.pointer[AUXMAC_BEGIN_MARKER] != '#' ||
>  	    obj->string.pointer[AUXMAC_END_MARKER] != '#') {
>  		pr_info("Invalid header for MAC address pass-through.\n");
> -		goto auxmacinvalid;
> +		return 0;
>  	}
> 
>  	if (strncmp(obj->string.pointer + AUXMAC_START, "XXXXXXXXXXXX", 
> AUXMAC_LEN) != 0)
> @@ -11014,13 +11006,7 @@ static int auxmac_init(struct ibm_init_struct 
> *iibm)
>  	else
>  		strscpy(auxmac, "disabled", sizeof(auxmac));
> 
> -free:
> -	kfree(obj);
>  	return 0;
> -
> -auxmacinvalid:
> -	strscpy(auxmac, "unavailable", sizeof(auxmac));
> -	goto free;
>  }
> 
>  static struct ibm_struct auxmac_data = {
> -- 
> 2.55.0.679.g6767b8d81c-goog

Another kernel implementation I didn't know about.
It all looks good to me, and gives some nice clean-up. Thanks

Reviewed-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx>
Mark