[PATCH 2/3] wifi: mt76: mt7925: validate debug message lengths

[Jiale Yao <yaojiale02@163.com>]

The debug message event handler removes the event prefix and accesses the
message header without checking the skb length. It also subtracts the
fixed header from the firmware-provided length without checking for an
underflow and trusts the string length. A truncated event can therefore
cause out-of-bounds reads while formatting firmware logs.

Validate the event prefix, fixed fields, declared message extent and each
format-specific payload before reading them.

Fixes: c948b5da6bbe ("wifi: mt76: mt7925: add Mediatek Wi-Fi7 driver for mt7925 chips")
Cc: stable@vger.kernel.org
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 .../net/wireless/mediatek/mt76/mt7925/mcu.c   | 24 +++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
index 26cdb3f0a98a..c612fda55eb7 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
@@ -596,8 +596,14 @@ mt7925_mcu_uni_debug_msg_event(struct mt792x_dev *dev, struct sk_buff *skb)
 			} __packed txt;
 		};
 	} __packed * hdr;
+	u16 msg_len;
 
+	if (skb->len < sizeof(struct mt7925_mcu_rxd) + 4)
+		return;
 	skb_pull(skb, sizeof(struct mt7925_mcu_rxd) + 4);
+	if (skb->len < offsetof(struct mt7925_uni_debug_msg, idx))
+		return;
+
 	hdr = (struct mt7925_uni_debug_msg *)skb->data;
 
 	if (hdr->id == 0x28) {
@@ -608,19 +614,28 @@ mt7925_mcu_uni_debug_msg_event(struct mt792x_dev *dev, struct sk_buff *skb)
 		return;
 	}
 
+	msg_len = le16_to_cpu(hdr->len);
+	if (msg_len < offsetof(struct mt7925_uni_debug_msg, idx) ||
+	    msg_len > skb->len)
+		return;
+
 	if (hdr->type == 0) { /* idx log */
 		int i, ret, len = PAGE_SIZE - 1, nr_val;
-		struct page *page = dev_alloc_pages(get_order(len));
+		struct page *page;
 		__le32 *val;
 		char *buf, *cur;
 
+		if (msg_len < sizeof(*hdr))
+			return;
+
+		page = dev_alloc_pages(get_order(len));
 		if (!page)
 			return;
 
 		buf = page_address(page);
 		cur = buf;
 
-		nr_val = (le16_to_cpu(hdr->len) - sizeof(*hdr)) / 4;
+		nr_val = (msg_len - sizeof(*hdr)) / sizeof(*val);
 		val = (__le32 *)hdr->idx.data;
 		for (i = 0; i < nr_val && len > 0; i++) {
 			ret = snprintf(cur, len, "0x%x,", le32_to_cpu(val[i]));
@@ -635,6 +650,11 @@ mt7925_mcu_uni_debug_msg_event(struct mt792x_dev *dev, struct sk_buff *skb)
 				   le32_to_cpu(hdr->idx.idx), nr_val, buf);
 		put_page(page);
 	} else if (hdr->type == 2) { /* str log */
+		if (msg_len < offsetof(struct mt7925_uni_debug_msg, txt.data) ||
+		    hdr->txt.len > msg_len - offsetof(struct mt7925_uni_debug_msg,
+						       txt.data))
+			return;
+
 		wiphy_info(mt76_hw(dev)->wiphy, "%.*s", hdr->txt.len, hdr->txt.data);
 	}
 }
-- 
2.34.1