[PATCH mt76-next 06/11] wifi: mt76: connac: validate the RAM firmware region table

[Felix Fietkau <nbd@nbd.name>]

mt76_connac2_load_ram() and mt76_connac3_load_phy_ram() only check that
the firmware image holds the trailer. The region table in front of the
trailer and the region lengths come from the image and are not checked
against its size. A malformed image makes the driver read past the
image and send that data to the device.

Add mt76_connac2_fw_check(), which checks that the region table and the
sum of the region lengths fit in the image, and reject an image that
fails it.

Fixes: e57b7901469f ("mt76: add mac80211 driver for MT7915 PCIe-based chipsets")
Fixes: 1c099ab44727 ("mt76: mt7921: add MCU support")
Fixes: 4f8ded4d5f0e ("wifi: mt76: mt7925: add MT7928 FWDL support")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 .../wireless/mediatek/mt76/mt76_connac_mcu.c  | 39 +++++++++++++++++--
 .../wireless/mediatek/mt76/mt76_connac_mcu.h  |  3 ++
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
index 9bdfff24b702..88cdc8083bae 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
@@ -3042,6 +3042,39 @@ s8 mt76_connac_get_rate_power_limit(struct mt76_phy *phy,
 }
 EXPORT_SYMBOL_GPL(mt76_connac_get_rate_power_limit);
 
+int mt76_connac2_fw_check(const struct firmware *fw, size_t *data_len)
+{
+	const struct mt76_connac2_fw_region *region;
+	const struct mt76_connac2_fw_trailer *hdr;
+	size_t avail, len = 0;
+	int i;
+
+	if (!fw || !fw->data || fw->size < sizeof(*hdr))
+		return -EINVAL;
+
+	hdr = (const void *)(fw->data + fw->size - sizeof(*hdr));
+	avail = fw->size - sizeof(*hdr);
+	if (hdr->n_region > avail / sizeof(*region))
+		return -EINVAL;
+
+	avail -= hdr->n_region * sizeof(*region);
+	region = (const void *)(fw->data + avail);
+	for (i = 0; i < hdr->n_region; i++) {
+		u32 region_len = le32_to_cpu(region[i].len);
+
+		if (region_len > avail - len)
+			return -EINVAL;
+
+		len += region_len;
+	}
+
+	if (data_len)
+		*data_len = len;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mt76_connac2_fw_check);
+
 static int
 mt76_connac_mcu_send_ram_firmware(struct mt76_dev *dev,
 				  const struct mt76_connac2_fw_trailer *hdr,
@@ -3155,7 +3188,7 @@ int mt76_connac2_load_ram(struct mt76_dev *dev, const char *fw_wm,
 	if (ret)
 		return ret;
 
-	if (!fw || !fw->data || fw->size < sizeof(*hdr)) {
+	if (mt76_connac2_fw_check(fw, NULL)) {
 		dev_err(dev->dev, "Invalid firmware\n");
 		ret = -EINVAL;
 		goto out;
@@ -3184,7 +3217,7 @@ int mt76_connac2_load_ram(struct mt76_dev *dev, const char *fw_wm,
 	if (ret)
 		return ret;
 
-	if (!fw || !fw->data || fw->size < sizeof(*hdr)) {
+	if (mt76_connac2_fw_check(fw, NULL)) {
 		dev_err(dev->dev, "Invalid firmware\n");
 		ret = -EINVAL;
 		goto out;
@@ -3221,7 +3254,7 @@ int mt76_connac3_load_phy_ram(struct mt76_dev *dev, const char *fw_name)
 	if (ret)
 		return ret;
 
-	if (!fw || !fw->data || fw->size < sizeof(*hdr)) {
+	if (mt76_connac2_fw_check(fw, NULL)) {
 		dev_err(dev->dev, "Invalid PHY firmware\n");
 		ret = -EINVAL;
 		goto out;
diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.h b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.h
index 74e37d722710..755c83f95f27 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.h
+++ b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.h
@@ -6,6 +6,8 @@
 
 #include "mt76_connac.h"
 
+struct firmware;
+
 #define FW_FEATURE_SET_ENCRYPT		BIT(0)
 #define FW_FEATURE_SET_KEY_IDX		GENMASK(2, 1)
 #define FW_FEATURE_ENCRY_MODE		BIT(4)
@@ -2147,6 +2149,7 @@ int mt76_connac_mcu_del_wtbl_all(struct mt76_dev *dev);
 int mt76_connac_mcu_rdd_cmd(struct mt76_dev *dev, int cmd, u8 index,
 			    u8 rx_sel, u8 val);
 int mt76_connac_mcu_sta_wed_update(struct mt76_dev *dev, struct sk_buff *skb);
+int mt76_connac2_fw_check(const struct firmware *fw, size_t *data_len);
 int mt76_connac2_load_ram(struct mt76_dev *dev, const char *fw_wm,
 			  const char *fw_wa);
 int mt76_connac3_load_phy_ram(struct mt76_dev *dev, const char *fw_name);
-- 
2.47.3