[PATCH 4/7] wifi: mt76: mt7996: validate free-block response length

[Jiale Yao <yaojiale02@163.com>]

The EFUSE free-block query reads a byte after an eight-byte prefix
without checking the firmware response length. A truncated response can
cause an out-of-bounds read.

Require the prefix and block-count byte before accessing the response.

Fixes: f456e1f56c4c ("wifi: mt76: add external EEPROM support for mt799x chipsets")
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 drivers/net/wireless/mediatek/mt76/mt7996/mcu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
index eb868c2d5108..c70d7ad3148c 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
@@ -4516,6 +4516,10 @@ int mt7996_mcu_get_efuse_free_block(struct mt7996_dev *dev, u8 *block_num)
 					sizeof(req), true, &skb);
 	if (ret)
 		return ret;
+	if (skb->len < 8 + sizeof(*block_num)) {
+		dev_kfree_skb(skb);
+		return -EINVAL;
+	}
 
 	*block_num = *(u8 *)(skb->data + 8);
 	dev_kfree_skb(skb);
-- 
2.34.1