[PATCH v3 2/2] HID: intel-thc-hid: quicki2c: validate ACPI buffer length before memcpy

[Tristan Madani <tristmd@gmail.com>]

From: Tristan Madani <tristan@talencesecurity.com>

quicki2c_acpi_get_dsm_property() copies firmware-returned ACPI buffers
into caller-provided structures without verifying the buffer length.
Malformed or short ACPI tables could cause an out-of-bounds read from
the firmware buffer, and oversized responses could overflow the
destination struct.

Additionally, quicki2c_acpi_get_dsd_property() does not validate the
returned ACPI object type before accessing buffer fields, and does not
free the allocated ACPI buffer on the success path, leaking memory on
every call.

Add a buf_size parameter to both ACPI helper functions and reject
responses larger than the destination buffer. Accept shorter responses
to handle firmware that returns buffers without struct tail padding
(e.g. ISUB tables returning 177 or 145 bytes for a 184-byte struct).
Zero-initialize caller stack structures so fields beyond the firmware
response length are deterministic. Add the missing type check and
kfree to the DSD helper.

Fixes: 5282e45ccbfa ("HID: intel-thc-hid: intel-quicki2c: Add THC QuickI2C ACPI interfaces")
Cc: stable@vger.kernel.org
Reviewed-by: Even Xu <even.xu@intel.com>
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
 .../intel-quicki2c/pci-quicki2c.c             | 42 ++++++++++++++-----
 1 file changed, 31 insertions(+), 11 deletions(-)

diff --git a/drivers/hid/intel-thc-hid/intel-quicki2c/pci-quicki2c.c b/drivers/hid/intel-thc-hid/intel-quicki2c/pci-quicki2c.c
index 2537288b50261..064195b7f4669 100644
--- a/drivers/hid/intel-thc-hid/intel-quicki2c/pci-quicki2c.c
+++ b/drivers/hid/intel-thc-hid/intel-quicki2c/pci-quicki2c.c
@@ -56,13 +56,15 @@ static const struct acpi_gpio_mapping quicki2c_gpios[] = {
  * @func: ACPI method's function number
  * @type: ACPI parameter's data type
  * @prop_buf: Point to return buffer
+ * @buf_size: Size of @prop_buf in bytes (0 to skip length check)
  *
  * This is a helper function for device to query its ACPI DSM parameters.
  *
  * Return: 0 if success or ENODEV on failure.
  */
 static int quicki2c_acpi_get_dsm_property(struct acpi_device *adev, const guid_t *guid,
-					  u64 rev, u64 func, acpi_object_type type, void *prop_buf)
+					  u64 rev, u64 func, acpi_object_type type,
+					  void *prop_buf, size_t buf_size)
 {
 	acpi_handle handle = acpi_device_handle(adev);
 	union acpi_object *obj;
@@ -75,10 +77,15 @@ static int quicki2c_acpi_get_dsm_property(struct acpi_device *adev, const guid_t
 		return -ENODEV;
 	}
 
-	if (type == ACPI_TYPE_INTEGER)
+	if (type == ACPI_TYPE_INTEGER) {
 		*(u32 *)prop_buf = (u32)obj->integer.value;
-	else if (type == ACPI_TYPE_BUFFER)
+	} else if (type == ACPI_TYPE_BUFFER) {
+		if (buf_size > 0 && obj->buffer.length > buf_size) {
+			ACPI_FREE(obj);
+			return -ENOSPC;
+		}
 		memcpy(prop_buf, obj->buffer.pointer, obj->buffer.length);
+	}
 
 	ACPI_FREE(obj);
 
@@ -91,13 +98,15 @@ static int quicki2c_acpi_get_dsm_property(struct acpi_device *adev, const guid_t
  * @dsd_method_name: ACPI method's property name
  * @type: ACPI parameter's data type
  * @prop_buf: Point to return buffer
+ * @buf_size: Size of @prop_buf in bytes (0 to skip length check)
  *
  * This is a helper function for device to query its ACPI DSD parameters.
  *
  * Return: 0 if success or ENODEV on failed.
  */
 static int quicki2c_acpi_get_dsd_property(struct acpi_device *adev, acpi_string dsd_method_name,
-					  acpi_object_type type, void *prop_buf)
+					  acpi_object_type type, void *prop_buf,
+					  size_t buf_size)
 {
 	acpi_handle handle = acpi_device_handle(adev);
 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
@@ -113,7 +122,16 @@ static int quicki2c_acpi_get_dsd_property(struct acpi_device *adev, acpi_string
 
 	ret_obj = buffer.pointer;
 
+	if (ret_obj->type != type) {
+		kfree(buffer.pointer);
+		return -EINVAL;
+	}
+	if (buf_size > 0 && ret_obj->buffer.length > buf_size) {
+		kfree(buffer.pointer);
+		return -ENOSPC;
+	}
 	memcpy(prop_buf, ret_obj->buffer.pointer, ret_obj->buffer.length);
+	kfree(buffer.pointer);
 
 	return 0;
 }
@@ -129,8 +147,8 @@ static int quicki2c_acpi_get_dsd_property(struct acpi_device *adev, acpi_string
 static int quicki2c_get_acpi_resources(struct quicki2c_device *qcdev)
 {
 	struct acpi_device *adev = ACPI_COMPANION(qcdev->dev);
-	struct quicki2c_subip_acpi_parameter i2c_param;
-	struct quicki2c_subip_acpi_config i2c_config;
+	struct quicki2c_subip_acpi_parameter i2c_param = {};
+	struct quicki2c_subip_acpi_config i2c_config = {};
 	u32 hid_desc_addr;
 	int ret = -EINVAL;
 
@@ -145,7 +163,7 @@ static int quicki2c_get_acpi_resources(struct quicki2c_device *qcdev)
 					     QUICKI2C_ACPI_REVISION_NUM,
 					     QUICKI2C_ACPI_FUNC_NUM_HID_DESC_ADDR,
 					     ACPI_TYPE_INTEGER,
-					     &hid_desc_addr);
+					     &hid_desc_addr, 0);
 	if (ret)
 		return ret;
 
@@ -155,7 +173,7 @@ static int quicki2c_get_acpi_resources(struct quicki2c_device *qcdev)
 					     QUICKI2C_ACPI_REVISION_NUM,
 					     QUICKI2C_ACPI_FUNC_NUM_ACTIVE_LTR_VAL,
 					     ACPI_TYPE_INTEGER,
-					     &qcdev->active_ltr_val);
+					     &qcdev->active_ltr_val, 0);
 	if (ret)
 		return ret;
 
@@ -163,12 +181,13 @@ static int quicki2c_get_acpi_resources(struct quicki2c_device *qcdev)
 					     QUICKI2C_ACPI_REVISION_NUM,
 					     QUICKI2C_ACPI_FUNC_NUM_LP_LTR_VAL,
 					     ACPI_TYPE_INTEGER,
-					     &qcdev->low_power_ltr_val);
+					     &qcdev->low_power_ltr_val, 0);
 	if (ret)
 		return ret;
 
 	ret = quicki2c_acpi_get_dsd_property(adev, QUICKI2C_ACPI_METHOD_NAME_ICRS,
-					     ACPI_TYPE_BUFFER, &i2c_param);
+					     ACPI_TYPE_BUFFER, &i2c_param,
+					     sizeof(i2c_param));
 	if (ret)
 		return ret;
 
@@ -180,7 +199,8 @@ static int quicki2c_get_acpi_resources(struct quicki2c_device *qcdev)
 	qcdev->i2c_config.target_addr = i2c_param.device_address;
 
 	ret = quicki2c_acpi_get_dsd_property(adev, QUICKI2C_ACPI_METHOD_NAME_ISUB,
-					     ACPI_TYPE_BUFFER, &i2c_config);
+					     ACPI_TYPE_BUFFER, &i2c_config,
+					     sizeof(i2c_config));
 	if (ret)
 		return ret;
 
-- 
2.47.3