[PATCH 2/2] wifi: mt76: mt7915: validate skb length in txpower SKU query

[Aviel Zohar <avielzohar123@gmail.com>]

In mt7915_mcu_get_txpower_sku(), the response skb from
mt76_mcu_send_and_get_msg() is used in memcpy without validating
its length:

For TX_POWER_INFO_RATE:
  memcpy(res, skb->data + 4, sizeof(res));

where sizeof(res) is MT7915_SKU_RATE_NUM * 2 = 322 bytes.

For TX_POWER_INFO_PATH:
  memcpy(txpower, skb->data + 4, len);

In both cases, if the firmware returns a response shorter than
the expected size, the memcpy reads beyond the skb data buffer.
The data surfaces to userspace via debugfs (txpower_sku and
txpower_path).

Add length checks for both code paths before the memcpy.

Signed-off-by: Aviel Zohar <avielzohar123@gmail.com>
---
 drivers/net/wireless/mediatek/mt76/mt7915/mcu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
@@ -3532,10 +3532,18 @@
 	if (category == TX_POWER_INFO_RATE) {
 		s8 res[MT7915_SKU_RATE_NUM][2];
 
+		if (skb->len < sizeof(res) + 4) {
+			dev_kfree_skb(skb);
+			return -EINVAL;
+		}
 		memcpy(res, skb->data + 4, sizeof(res));
 		for (i = 0; i < len; i++)
 			txpower[i] = res[i][req.band_idx];
 	} else if (category == TX_POWER_INFO_PATH) {
+		if (skb->len < len + 4) {
+			dev_kfree_skb(skb);
+			return -EINVAL;
+		}
 		memcpy(txpower, skb->data + 4, len);
 	}