[PATCH] ALSA: usb-audio: caiaq: validate EP1 reply lengths

[Pengpeng Hou]

usb_ep1_command_reply_dispatch() uses buf[0] as a command byte and then
reads command-specific fixed items from the same URB buffer. Several
paths use buf + 1, buf[1], buf[2], or buf + 3 without first proving that
urb->actual_length contains those bytes.

Add per-command length checks, use a payload length derived from the
bytes after the command byte for the control-state copy, and reject short
analog input payloads before the input helper reads fixed offsets from
the EP1 reply.

Signed-off-by: Pengpeng Hou <pengpeng@xxxxxxxxxxx>
---
diff --git a/sound/usb/caiaq/device.c b/sound/usb/caiaq/device.c
index b20aae0..a16e592 100644
--- a/sound/usb/caiaq/device.c
+++ b/sound/usb/caiaq/device.c
@@ -134,14 +134,22 @@ static void usb_ep1_command_reply_dispatch (struct urb* urb)
 	struct device *dev = &urb->dev->dev;
 	struct snd_usb_caiaqdev *cdev = urb->context;
 	unsigned char *buf = urb->transfer_buffer;
+	unsigned int payload_len;
+	unsigned int copy_len;
 
 	if (urb->status || !cdev) {
 		dev_warn(dev, "received EP1 urb->status = %i\n", urb->status);
 		return;
 	}
+	if (urb->actual_length < 1)
+		return;
+
+	payload_len = urb->actual_length - 1;
 
 	switch(buf[0]) {
 	case EP1_CMD_GET_DEVICE_INFO:
+		if (payload_len < sizeof(struct caiaq_device_spec))
+			break;
 	 	memcpy(&cdev->spec, buf+1, sizeof(struct caiaq_device_spec));
 		cdev->spec.fw_version = le16_to_cpu(cdev->spec.fw_version);
 		dev_dbg(dev, "device spec (firmware %d): audio: %d in, %d out, "
@@ -157,18 +165,21 @@ static void usb_ep1_command_reply_dispatch (struct urb* urb)
 		wake_up(&cdev->ep1_wait_queue);
 		break;
 	case EP1_CMD_AUDIO_PARAMS:
+		if (payload_len < 1)
+			break;
 		cdev->audio_parm_answer = buf[1];
 		wake_up(&cdev->ep1_wait_queue);
 		break;
 	case EP1_CMD_MIDI_READ:
+		if (urb->actual_length < 3 || urb->actual_length - 3 < buf[2])
+			break;
 		snd_usb_caiaq_midi_handle_input(cdev, buf[1], buf + 3, buf[2]);
 		break;
 	case EP1_CMD_READ_IO:
 		if (cdev->chip.usb_id ==
 			USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_AUDIO8DJ)) {
-			if (urb->actual_length > sizeof(cdev->control_state))
-				urb->actual_length = sizeof(cdev->control_state);
-			memcpy(cdev->control_state, buf + 1, urb->actual_length);
+			copy_len = min_t(unsigned int, payload_len, sizeof(cdev->control_state));
+			memcpy(cdev->control_state, buf + 1, copy_len);
 			wake_up(&cdev->ep1_wait_queue);
 			break;
 		}
diff --git a/sound/usb/caiaq/input.c b/sound/usb/caiaq/input.c
index eabbf41..8d92433 100644
--- a/sound/usb/caiaq/input.c
+++ b/sound/usb/caiaq/input.c
@@ -203,6 +203,8 @@ static void snd_caiaq_input_read_analog(struct snd_usb_caiaqdev *cdev,
 
 	switch (cdev->chip.usb_id) {
 	case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_RIGKONTROL2):
+		if (len < 6)
+			return;
 		snd_caiaq_input_report_abs(cdev, ABS_X, buf, 2);
 		snd_caiaq_input_report_abs(cdev, ABS_Y, buf, 0);
 		snd_caiaq_input_report_abs(cdev, ABS_Z, buf, 1);
@@ -210,11 +212,15 @@ static void snd_caiaq_input_read_analog(struct snd_usb_caiaqdev *cdev,
 	case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_RIGKONTROL3):
 	case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_KORECONTROLLER):
 	case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_KORECONTROLLER2):
+		if (len < 6)
+			return;
 		snd_caiaq_input_report_abs(cdev, ABS_X, buf, 0);
 		snd_caiaq_input_report_abs(cdev, ABS_Y, buf, 1);
 		snd_caiaq_input_report_abs(cdev, ABS_Z, buf, 2);
 		break;
 	case USB_ID(USB_VID_NATIVEINSTRUMENTS, USB_PID_TRAKTORKONTROLX1):
+		if (len < 16)
+			return;
 		snd_caiaq_input_report_abs(cdev, ABS_HAT0X, buf, 4);
 		snd_caiaq_input_report_abs(cdev, ABS_HAT0Y, buf, 2);
 		snd_caiaq_input_report_abs(cdev, ABS_HAT1X, buf, 6);