[PATCH v2 29/33] HID: logitech-hidpp: use __free(kfree) for temporary allocations

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Managing short-lived heap allocations manually with explicit kfree()
calls adds boilerplate cleanup paths and forces callers to hold
temporary return variables across calls.

Convert temporary message and device-name allocations in command helpers
and device initialization paths to use __free(kfree) with no_free_ptr()
ownership transfer where the buffer is returned to callers.

Tested-by: Gideon Heinz <gideonheinz02@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/hid/hid-logitech-hidpp.c | 44 +++++++++++++---------------------------
 1 file changed, 14 insertions(+), 30 deletions(-)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 8f2a9d3e0f74..67b4f1112168 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -401,18 +401,15 @@ static int hidpp_send_fap_command_sync(struct hidpp_device *hidpp,
 	u8 feat_index, u8 funcindex_clientid, u8 *params, int param_count,
 	struct hidpp_report *response)
 {
-	struct hidpp_report *message;
-	int ret;
-
-	if (param_count > sizeof(message->fap.params)) {
+	if (param_count > sizeof_field(struct hidpp_report, fap.params)) {
 		hid_dbg(hidpp->hid_dev,
 			"Invalid number of parameters passed to command (%d != %llu)\n",
 			param_count,
-			(unsigned long long) sizeof(message->fap.params));
+			(unsigned long long)sizeof_field(struct hidpp_report, fap.params));
 		return -EINVAL;
 	}
 
-	message = kzalloc_obj(struct hidpp_report);
+	struct hidpp_report *message __free(kfree) = kzalloc_obj(*message);
 	if (!message)
 		return -ENOMEM;
 
@@ -424,9 +421,7 @@ static int hidpp_send_fap_command_sync(struct hidpp_device *hidpp,
 	message->fap.funcindex_clientid = funcindex_clientid | LINUX_KERNEL_SW_ID;
 	memcpy(&message->fap.params, params, param_count);
 
-	ret = hidpp_send_message_sync(hidpp, message, response);
-	kfree(message);
-	return ret;
+	return hidpp_send_message_sync(hidpp, message, response);
 }
 
 /*
@@ -437,8 +432,7 @@ static int hidpp_send_rap_command_sync(struct hidpp_device *hidpp_dev,
 	u8 report_id, u8 sub_id, u8 reg_address, u8 *params, int param_count,
 	struct hidpp_report *response)
 {
-	struct hidpp_report *message;
-	int ret, max_count;
+	int max_count;
 
 	/* Send as long report if short reports are not supported. */
 	if (report_id == REPORT_ID_HIDPP_SHORT &&
@@ -462,7 +456,7 @@ static int hidpp_send_rap_command_sync(struct hidpp_device *hidpp_dev,
 	if (param_count > max_count)
 		return -EINVAL;
 
-	message = kzalloc_obj(struct hidpp_report);
+	struct hidpp_report *message __free(kfree) = kzalloc_obj(*message);
 	if (!message)
 		return -ENOMEM;
 	message->report_id = report_id;
@@ -470,9 +464,7 @@ static int hidpp_send_rap_command_sync(struct hidpp_device *hidpp_dev,
 	message->rap.reg_address = reg_address;
 	memcpy(&message->rap.params, params, param_count);
 
-	ret = hidpp_send_message_sync(hidpp_dev, message, response);
-	kfree(message);
-	return ret;
+	return hidpp_send_message_sync(hidpp_dev, message, response);
 }
 
 static inline bool hidpp_match_answer(struct hidpp_report *question,
@@ -919,7 +911,6 @@ static int hidpp_unifying_get_serial(struct hidpp_device *hidpp,
 static int hidpp_unifying_init(struct hidpp_device *hidpp)
 {
 	struct hid_device *hdev = hidpp->hid_dev;
-	const char *name;
 	u8 serial[HIDPP_SERIAL_LENGTH];
 	int ret;
 
@@ -930,14 +921,13 @@ static int hidpp_unifying_init(struct hidpp_device *hidpp)
 	snprintf(hdev->uniq, sizeof(hdev->uniq), "%4phD", serial);
 	dbg_hid("HID++ Unifying: Got serial: %s\n", hdev->uniq);
 
-	name = hidpp_unifying_get_name(hidpp);
+	char *name __free(kfree) = hidpp_unifying_get_name(hidpp);
 	if (!name)
 		return -EIO;
 
 	snprintf(hdev->name, sizeof(hdev->name), "%s", name);
 	dbg_hid("HID++ Unifying: Got name: %s\n", name);
 
-	kfree(name);
 	return 0;
 }
 
@@ -1131,7 +1121,6 @@ static char *hidpp_get_device_name(struct hidpp_device *hidpp)
 {
 	u8 feature_index;
 	u8 __name_length;
-	char *name;
 	unsigned index = 0;
 	int ret;
 
@@ -1145,7 +1134,7 @@ static char *hidpp_get_device_name(struct hidpp_device *hidpp)
 	if (ret)
 		return NULL;
 
-	name = kzalloc(__name_length + 1, GFP_KERNEL);
+	char *name __free(kfree) = kzalloc(__name_length + 1, GFP_KERNEL);
 	if (!name)
 		return NULL;
 
@@ -1153,17 +1142,15 @@ static char *hidpp_get_device_name(struct hidpp_device *hidpp)
 		ret = hidpp_devicenametype_get_device_name(hidpp,
 			feature_index, index, name + index,
 			__name_length - index);
-		if (ret <= 0) {
-			kfree(name);
+		if (ret <= 0)
 			return NULL;
-		}
 		index += ret;
 	}
 
 	/* include the terminating '\0' */
 	hidpp_prefix_name(&name, __name_length + 1);
 
-	return name;
+	return no_free_ptr(name);
 }
 
 /* -------------------------------------------------------------------------- */
@@ -4328,17 +4315,15 @@ static int hidpp_initialize_battery(struct hidpp_device *hidpp)
 static void hidpp_non_unifying_init(struct hidpp_device *hidpp)
 {
 	struct hid_device *hdev = hidpp->hid_dev;
-	char *name;
 
 	/* Bluetooth devices already have their serialnr set */
 	if (hid_is_usb(hdev))
 		hidpp_serial_init(hidpp);
 
-	name = hidpp_get_device_name(hidpp);
+	char *name __free(kfree) = hidpp_get_device_name(hidpp);
 	if (name) {
 		dbg_hid("HID++: Got name: %s\n", name);
 		snprintf(hdev->name, sizeof(hdev->name), "%s", name);
-		kfree(name);
 	}
 }
 
@@ -4385,7 +4370,7 @@ static void hidpp_connect_event(struct work_struct *work)
 	struct hidpp_device *hidpp = container_of(work, struct hidpp_device, work);
 	struct hid_device *hdev = hidpp->hid_dev;
 	struct input_dev *input;
-	char *name, *devm_name;
+	char *devm_name;
 	int ret;
 
 	/* Get device version to check if it is connected */
@@ -4443,11 +4428,10 @@ static void hidpp_connect_event(struct work_struct *work)
 	}
 
 	if (hidpp->name == hdev->name && hidpp->protocol_major >= 2) {
-		name = hidpp_get_device_name(hidpp);
+		char *name __free(kfree) = hidpp_get_device_name(hidpp);
 		if (name) {
 			devm_name = devm_kasprintf(&hdev->dev, GFP_KERNEL,
 						   "%s", name);
-			kfree(name);
 			if (!devm_name)
 				return;
 

-- 
2.56.0.542.g3ef89b7020-goog