[PATCH 2/2] wifi: mt76: mt7615: usb: fix source overread in mt7663u_copy

[Jiale Yao <yaojiale02@163.com>]

mt7663u_copy() rounds up len to a multiple of four and uses the rounded
length as the bound for memcpy() from the source buffer. When the
caller's length is not four-byte aligned, the final copy reads up to
three bytes past the source buffer.

Keep the original length for the source copy and zero the remaining
bytes in the transmit buffer so that the hardware access width remains
four-byte aligned.

Fixes: 6cb596ba84e3 ("mt76: usb: introduce __mt76u_init utility routine")
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 drivers/net/wireless/mediatek/mt76/mt7615/usb.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/usb.c b/drivers/net/wireless/mediatek/mt76/mt7615/usb.c
index bab7b91f14be..3629e3d9bf47 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7615/usb.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7615/usb.c
@@ -58,15 +58,22 @@ static void mt7663u_copy(struct mt76_dev *dev, u32 offset,
 			 const void *data, int len)
 {
 	struct mt76_usb *usb = &dev->usb;
-	int ret, i = 0, batch_len;
 	const u8 *val = data;
+	int len_aligned;
+	int batch_len;
+	int copy_len;
+	int ret;
+	int i = 0;
 
-	len = round_up(len, 4);
+	len_aligned = round_up(len, 4);
 
 	mutex_lock(&usb->usb_ctrl_mtx);
-	while (i < len) {
-		batch_len = min_t(int, usb->data_len, len - i);
-		memcpy(usb->data, val + i, batch_len);
+	while (i < len_aligned) {
+		batch_len = min_t(int, usb->data_len, len_aligned - i);
+		copy_len = min_t(int, batch_len, len - i);
+		memcpy(usb->data, val + i, copy_len);
+		if (copy_len < batch_len)
+			memset(usb->data + copy_len, 0, batch_len - copy_len);
 		ret = __mt76u_vendor_request(dev, MT_VEND_WRITE_EXT,
 					     USB_DIR_OUT | USB_TYPE_VENDOR,
 					     (offset + i) >> 16, offset + i,
-- 
2.34.1