[PATCH 1/3] Bluetooth: btmtk: Fix short read errors in btmtk_usb_uhw_reg_read()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

If btmtk_usb_uhw_reg_read() gets a "short" read from a device, it will
accidentally treat that as a "real" read and populate the returned value
with some unknown and probably totally invalid data.

Fix this logic error up by calling usb_control_msg_recv() which
guarantees a "full" read happens, and then simplify the error checking
for when btmtk_usb_uhw_reg_read() is called.

Note, one caller of btmtk_usb_uhw_reg_read() does not check the return
value, but as we pre-initialize the return value as 0, an incorrect read
will not do anything wrong.

Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/bluetooth/btmtk.c | 50 +++++++++++++++++++++--------------------------
 1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
index 02a96342e964..6f060e4433db 100644
--- a/drivers/bluetooth/btmtk.c
+++ b/drivers/bluetooth/btmtk.c
@@ -804,30 +804,24 @@ static int btmtk_usb_uhw_reg_write(struct hci_dev *hdev, u32 reg, u32 val)
 static int btmtk_usb_uhw_reg_read(struct hci_dev *hdev, u32 reg, u32 *val)
 {
 	struct btmtk_data *data = hci_get_priv(hdev);
-	int pipe, err;
-	void *buf;
+	u8 buf[sizeof(u32)];
+	int err;
 
-	buf = kzalloc(4, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	pipe = usb_rcvctrlpipe(data->udev, 0);
-	err = usb_control_msg(data->udev, pipe, 0x01,
-			      0xDE,
-			      reg >> 16, reg & 0xffff,
-			      buf, 4, USB_CTRL_GET_TIMEOUT);
-	if (err < 0) {
+	*val = 0;
+	err = usb_control_msg_recv(data->udev, 0, 0x01,
+				   0xDE,
+				   reg >> 16, reg & 0xffff,
+				   buf, sizeof(buf), USB_CTRL_GET_TIMEOUT,
+				   GFP_KERNEL);
+	if (err) {
 		bt_dev_err(hdev, "Failed to read uhw reg(%d)", err);
-		goto err_free_buf;
+		return err;
 	}
 
 	*val = get_unaligned_le32(buf);
 	bt_dev_dbg(hdev, "reg=%x, value=0x%08x", reg, *val);
 
-err_free_buf:
-	kfree(buf);
-
-	return err;
+	return 0;
 }
 
 static int btmtk_usb_reg_read(struct hci_dev *hdev, u32 reg, u32 *val)
@@ -877,7 +871,7 @@ int btmtk_usb_subsys_reset(struct hci_dev *hdev, u32 dev_id)
 
 	if (dev_id == 0x7922) {
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_BT_SUBSYS_RST, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		val |= 0x00002020;
 		err = btmtk_usb_uhw_reg_write(hdev, MTK_BT_SUBSYS_RST, val);
@@ -887,7 +881,7 @@ int btmtk_usb_subsys_reset(struct hci_dev *hdev, u32 dev_id)
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_BT_SUBSYS_RST, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		val |= BIT(0);
 		err = btmtk_usb_uhw_reg_write(hdev, MTK_BT_SUBSYS_RST, val);
@@ -896,14 +890,14 @@ int btmtk_usb_subsys_reset(struct hci_dev *hdev, u32 dev_id)
 		msleep(100);
 	} else if (dev_id == 0x7925 || dev_id == 0x6639) {
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_BT_RESET_REG_CONNV3, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		val |= (1 << 5);
 		err = btmtk_usb_uhw_reg_write(hdev, MTK_BT_RESET_REG_CONNV3, val);
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_BT_RESET_REG_CONNV3, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		val &= 0xFFFF00FF;
 		val |= (1 << 13);
@@ -914,7 +908,7 @@ int btmtk_usb_subsys_reset(struct hci_dev *hdev, u32 dev_id)
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_BT_RESET_REG_CONNV3, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		val |= (1 << 0);
 		err = btmtk_usb_uhw_reg_write(hdev, MTK_BT_RESET_REG_CONNV3, val);
@@ -924,13 +918,13 @@ int btmtk_usb_subsys_reset(struct hci_dev *hdev, u32 dev_id)
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_UDMA_INT_STA_BT, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		err = btmtk_usb_uhw_reg_write(hdev, MTK_UDMA_INT_STA_BT1, 0x000000FF);
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_UDMA_INT_STA_BT1, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		msleep(100);
 	} else {
@@ -940,7 +934,7 @@ int btmtk_usb_subsys_reset(struct hci_dev *hdev, u32 dev_id)
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_BT_WDT_STATUS, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		/* Reset the bluetooth chip via USB interface. */
 		err = btmtk_usb_uhw_reg_write(hdev, MTK_BT_SUBSYS_RST, 1);
@@ -950,13 +944,13 @@ int btmtk_usb_subsys_reset(struct hci_dev *hdev, u32 dev_id)
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_UDMA_INT_STA_BT, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		err = btmtk_usb_uhw_reg_write(hdev, MTK_UDMA_INT_STA_BT1, 0x000000FF);
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_UDMA_INT_STA_BT1, &val);
-		if (err < 0)
+		if (err)
 			return err;
 		/* MT7921 need to delay 20ms between toggle reset bit */
 		msleep(20);
@@ -964,7 +958,7 @@ int btmtk_usb_subsys_reset(struct hci_dev *hdev, u32 dev_id)
 		if (err < 0)
 			return err;
 		err = btmtk_usb_uhw_reg_read(hdev, MTK_BT_SUBSYS_RST, &val);
-		if (err < 0)
+		if (err)
 			return err;
 	}
 

-- 
2.55.0