[PATCH 1/2] Bluetooth: btmtk: validate WMT event SKB length before struct access

[Siva Balasubramanian <sivakumar.bs@gmail.com>]

From: Tristan Madani <tristan@talencesecurity.com>

commit 634a4408c0615c523cf7531790f4f14a422b9206 upstream.

btmtk_usb_hci_wmt_sync() casts the WMT event response SKB data to
struct btmtk_hci_wmt_evt (7 bytes) and struct btmtk_hci_wmt_evt_funcc
(9 bytes) without first checking that the SKB contains enough data.
A short firmware response causes out-of-bounds reads from SKB tailroom.

Use skb_pull_data() to validate and advance past the base WMT event
header. For the FUNC_CTRL case, pull the additional status field bytes
before accessing them.

Fixes: d019930b0049 ("Bluetooth: btmtk: move btusb_mtk_hci_wmt_sync to btmtk.c")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 634a4408c0615c523cf7531790f4f14a422b9206)
Signed-off-by: Siva Balasubramanian <sivakumar.bs@gmail.com>
---
 drivers/bluetooth/btmtk.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
index ad8753dda826..5c6f4d4b2e7f 100644
--- a/drivers/bluetooth/btmtk.c
+++ b/drivers/bluetooth/btmtk.c
@@ -655,8 +655,13 @@ int btmtk_usb_hci_wmt_sync(struct hci_dev *hdev,
 	if (data->evt_skb == NULL)
 		goto err_free_wc;
 
-	/* Parse and handle the return WMT event */
-	wmt_evt = (struct btmtk_hci_wmt_evt *)data->evt_skb->data;
+	wmt_evt = skb_pull_data(data->evt_skb, sizeof(*wmt_evt));
+	if (!wmt_evt) {
+		bt_dev_err(hdev, "WMT event too short (%u bytes)",
+			   data->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);
@@ -672,6 +677,12 @@ int btmtk_usb_hci_wmt_sync(struct hci_dev *hdev,
 			status = BTMTK_WMT_PATCH_DONE;
 		break;
 	case BTMTK_WMT_FUNC_CTRL:
+		if (!skb_pull_data(data->evt_skb,
+				   sizeof(wmt_evt_funcc->status))) {
+			err = -EINVAL;
+			goto err_free_skb;
+		}
+
 		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;
-- 
2.34.1