[PATCH v2 3/3] Bluetooth: btmtksdio, btmtkuart: validate WMT event length before struct access

[Chris Lu <chris.lu@mediatek.com>]

btmtksdio.c and btmtkuart.c cast a received WMT event straight to
struct btmtk_hci_wmt_evt and read its op/flag fields without checking
the event is long enough to contain them, unlike btmtk.c. The
FUNC_CTRL case then further casts to struct btmtk_hci_wmt_evt_funcc
and reads its 2-byte status field, again without a length check.
Firmware that sends a short or malformed WMT event makes both drivers
read past the end of the received SKB.

Mirror btmtk.c: validate the base WMT header with skb_pull_data()
before touching any of its fields, and when a FUNC_CTRL event turns
out to be the short, header-only form (a plain enable/disable ack
with no status word), decode the result from the header's own flag
byte instead (0 = success, otherwise failure).

Verified setup on MT7920, MT7921, MT7922 and MT7925: no regression.

Fixes: 9aebfd4a2200 ("Bluetooth: mediatek: add support for MediaTek MT7663S and MT7668S SDIO devices")
Fixes: e0b67035a90b ("Bluetooth: mediatek: update the common setup between MT7622 and other devices")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Chris Lu <chris.lu@mediatek.com>
---
v2: No changes.

 drivers/bluetooth/btmtksdio.c | 20 +++++++++++++++++++-
 drivers/bluetooth/btmtkuart.c | 20 +++++++++++++++++++-
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/btmtksdio.c b/drivers/bluetooth/btmtksdio.c
index fe4ca9395aa3..a8ebcd0c005c 100644
--- a/drivers/bluetooth/btmtksdio.c
+++ b/drivers/bluetooth/btmtksdio.c
@@ -217,7 +217,14 @@ static int mtk_hci_wmt_sync(struct hci_dev *hdev,
 	}

 	/* Parse and handle the return WMT event */
-	wmt_evt = (struct btmtk_hci_wmt_evt *)bdev->evt_skb->data;
+	wmt_evt = skb_pull_data(bdev->evt_skb, sizeof(*wmt_evt));
+	if (!wmt_evt) {
+		bt_dev_err(hdev, "WMT event too short (%u bytes)",
+			   bdev->evt_skb->len);
+		err = -EINVAL;
+		goto err_free_skb;
+	}
+
 	if (wmt_evt->whdr.op != hdr->op) {
 		bt_dev_err(hdev, "Wrong op received %d expected %d",
 			   wmt_evt->whdr.op, hdr->op);
@@ -233,6 +240,17 @@ static int mtk_hci_wmt_sync(struct hci_dev *hdev,
 			status = BTMTK_WMT_PATCH_DONE;
 		break;
 	case BTMTK_WMT_FUNC_CTRL:
+		if (!skb_pull_data(bdev->evt_skb,
+				   sizeof(wmt_evt_funcc->status))) {
+			/* A plain enable/disable request is acked with just
+			 * the WMT header and no trailing status word; the
+			 * result is carried in the header's own flag byte.
+			 */
+			status = wmt_evt->whdr.flag ? BTMTK_WMT_ON_UNDONE :
+						       BTMTK_WMT_ON_DONE;
+			break;
+		}
+
 		wmt_evt_funcc = (struct btmtk_hci_wmt_evt_funcc *)wmt_evt;
 		if (be16_to_cpu(wmt_evt_funcc->status) == 0x404)
 			status = BTMTK_WMT_ON_DONE;
diff --git a/drivers/bluetooth/btmtkuart.c b/drivers/bluetooth/btmtkuart.c
index 27aa48ff3ac2..4af6fbbbd302 100644
--- a/drivers/bluetooth/btmtkuart.c
+++ b/drivers/bluetooth/btmtkuart.c
@@ -151,7 +151,14 @@ static int mtk_hci_wmt_sync(struct hci_dev *hdev,
 	}

 	/* Parse and handle the return WMT event */
-	wmt_evt = (struct btmtk_hci_wmt_evt *)bdev->evt_skb->data;
+	wmt_evt = skb_pull_data(bdev->evt_skb, sizeof(*wmt_evt));
+	if (!wmt_evt) {
+		bt_dev_err(hdev, "WMT event too short (%u bytes)",
+			   bdev->evt_skb->len);
+		err = -EINVAL;
+		goto err_free_wc;
+	}
+
 	if (wmt_evt->whdr.op != hdr->op) {
 		bt_dev_err(hdev, "Wrong op received %d expected %d",
 			   wmt_evt->whdr.op, hdr->op);
@@ -167,6 +174,17 @@ static int mtk_hci_wmt_sync(struct hci_dev *hdev,
 			status = BTMTK_WMT_PATCH_DONE;
 		break;
 	case BTMTK_WMT_FUNC_CTRL:
+		if (!skb_pull_data(bdev->evt_skb,
+				   sizeof(wmt_evt_funcc->status))) {
+			/* A plain enable/disable request is acked with just
+			 * the WMT header and no trailing status word; the
+			 * result is carried in the header's own flag byte.
+			 */
+			status = wmt_evt->whdr.flag ? BTMTK_WMT_ON_UNDONE :
+						       BTMTK_WMT_ON_DONE;
+			break;
+		}
+
 		wmt_evt_funcc = (struct btmtk_hci_wmt_evt_funcc *)wmt_evt;
 		if (be16_to_cpu(wmt_evt_funcc->status) == 0x404)
 			status = BTMTK_WMT_ON_DONE;
--
2.45.2