[PATCH v4 2/2] Bluetooth: btusb: use skb_pull to avoid unsafe access in QCA dump handling

[En-Wei Wu <en-wei.wu@xxxxxxxxxxxxx>]

Use skb_pull() and skb_pull_data() to safely parse QCA dump packets.

This avoids direct pointer math on skb->data, which could lead to
invalid access if the packet is shorter than expected.

Signed-off-by: En-Wei Wu <en-wei.wu@xxxxxxxxxxxxx>
---
 drivers/bluetooth/btusb.c | 98 ++++++++++++++++-----------------------
 1 file changed, 41 insertions(+), 57 deletions(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index f905780fcdea..031292ab766f 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -3017,8 +3017,6 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
 {
 	int ret = 0;
 	u8 pkt_type;
-	u8 *sk_ptr;
-	unsigned int sk_len;
 	u16 seqno;
 	u32 dump_size;
 
@@ -3027,18 +3025,8 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
 	struct usb_device *udev = btdata->udev;
 
 	pkt_type = hci_skb_pkt_type(skb);
-	sk_ptr = skb->data;
-	sk_len = skb->len;
+	dump_hdr = (struct qca_dump_hdr *)skb->data;
 
-	if (pkt_type == HCI_ACLDATA_PKT) {
-		sk_ptr += HCI_ACL_HDR_SIZE;
-		sk_len -= HCI_ACL_HDR_SIZE;
-	}
-
-	sk_ptr += HCI_EVENT_HDR_SIZE;
-	sk_len -= HCI_EVENT_HDR_SIZE;
-
-	dump_hdr = (struct qca_dump_hdr *)sk_ptr;
 	seqno = le16_to_cpu(dump_hdr->seqno);
 	if (seqno == 0) {
 		set_bit(BTUSB_HW_SSR_ACTIVE, &btdata->flags);
@@ -3058,16 +3046,15 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
 
 		btdata->qca_dump.ram_dump_size = dump_size;
 		btdata->qca_dump.ram_dump_seqno = 0;
-		sk_ptr += offsetof(struct qca_dump_hdr, data0);
-		sk_len -= offsetof(struct qca_dump_hdr, data0);
+
+		skb_pull(skb, offsetof(struct qca_dump_hdr, data0));
 
 		usb_disable_autosuspend(udev);
 		bt_dev_info(hdev, "%s memdump size(%u)\n",
 			    (pkt_type == HCI_ACLDATA_PKT) ? "ACL" : "event",
 			    dump_size);
 	} else {
-		sk_ptr += offsetof(struct qca_dump_hdr, data);
-		sk_len -= offsetof(struct qca_dump_hdr, data);
+		skb_pull(skb, offsetof(struct qca_dump_hdr, data));
 	}
 
 	if (!btdata->qca_dump.ram_dump_size) {
@@ -3087,7 +3074,6 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
 		return ret;
 	}
 
-	skb_pull(skb, skb->len - sk_len);
 	hci_devcd_append(hdev, skb);
 	btdata->qca_dump.ram_dump_seqno++;
 	if (seqno == QCA_LAST_SEQUENCE_NUM) {
@@ -3115,67 +3101,65 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
 /* Return: true if the ACL packet is a dump packet, false otherwise. */
 static bool acl_pkt_is_dump_qca(struct hci_dev *hdev, struct sk_buff *skb)
 {
-	u8 *sk_ptr;
-	unsigned int sk_len;
-
 	struct hci_event_hdr *event_hdr;
 	struct hci_acl_hdr *acl_hdr;
 	struct qca_dump_hdr *dump_hdr;
+	void *orig_data;
+	unsigned int orig_len;
 
-	sk_ptr = skb->data;
-	sk_len = skb->len;
+	orig_data = skb->data;
+	orig_len = skb->len;
 
-	acl_hdr = hci_acl_hdr(skb);
-	if (le16_to_cpu(acl_hdr->handle) != QCA_MEMDUMP_ACL_HANDLE)
-		return false;
-	sk_ptr += HCI_ACL_HDR_SIZE;
-	sk_len -= HCI_ACL_HDR_SIZE;
-	event_hdr = (struct hci_event_hdr *)sk_ptr;
+	acl_hdr = skb_pull_data(skb, sizeof(*acl_hdr));
+	if (!acl_hdr || (le16_to_cpu(acl_hdr->handle) != QCA_MEMDUMP_ACL_HANDLE))
+		goto restore_return;
 
-	if ((event_hdr->evt != HCI_VENDOR_PKT)
-		|| (event_hdr->plen != (sk_len - HCI_EVENT_HDR_SIZE)))
-		return false;
+	event_hdr = skb_pull_data(skb, sizeof(*event_hdr));
+	if (!event_hdr || (event_hdr->evt != HCI_VENDOR_PKT))
+		goto restore_return;
 
-	sk_ptr += HCI_EVENT_HDR_SIZE;
-	sk_len -= HCI_EVENT_HDR_SIZE;
-
-	dump_hdr = (struct qca_dump_hdr *)sk_ptr;
-	if ((sk_len < offsetof(struct qca_dump_hdr, data))
-		|| (dump_hdr->vse_class != QCA_MEMDUMP_VSE_CLASS)
-	    || (dump_hdr->msg_type != QCA_MEMDUMP_MSG_TYPE))
-		return false;
+	dump_hdr = (struct qca_dump_hdr *)skb->data;
+	if ((skb->len < sizeof(*dump_hdr)) ||
+	   (dump_hdr->vse_class != QCA_MEMDUMP_VSE_CLASS) ||
+	   (dump_hdr->msg_type != QCA_MEMDUMP_MSG_TYPE))
+		goto restore_return;
 
 	return true;
+
+restore_return:
+	skb->data = orig_data;
+	skb->len = orig_len;
+	return false;
 }
 
 /* Return: true if the event packet is a dump packet, false otherwise. */
 static bool evt_pkt_is_dump_qca(struct hci_dev *hdev, struct sk_buff *skb)
 {
-	u8 *sk_ptr;
-	unsigned int sk_len;
-
 	struct hci_event_hdr *event_hdr;
 	struct qca_dump_hdr *dump_hdr;
+	void *orig_data;
+	unsigned int orig_len;
 
-	sk_ptr = skb->data;
-	sk_len = skb->len;
+	orig_data = skb->data;
+	orig_len = skb->len;
 
-	event_hdr = hci_event_hdr(skb);
+	event_hdr = skb_pull_data(skb, sizeof(*event_hdr));
+	if (!event_hdr || (event_hdr->evt != HCI_VENDOR_PKT))
+		goto restore_return;
 
-	if ((event_hdr->evt != HCI_VENDOR_PKT)
-		|| (event_hdr->plen != (sk_len - HCI_EVENT_HDR_SIZE)))
-		return false;
+	dump_hdr = (struct qca_dump_hdr *)skb->data;
+	if ((skb->len < sizeof(*dump_hdr)) ||
+	   (dump_hdr->vse_class != QCA_MEMDUMP_VSE_CLASS) ||
+	   (dump_hdr->msg_type != QCA_MEMDUMP_MSG_TYPE))
+		goto restore_return;
 
-	sk_ptr += HCI_EVENT_HDR_SIZE;
-	sk_len -= HCI_EVENT_HDR_SIZE;
+	return true;
 
-	dump_hdr = (struct qca_dump_hdr *)sk_ptr;
-	if ((sk_len < offsetof(struct qca_dump_hdr, data))
-		|| (dump_hdr->vse_class != QCA_MEMDUMP_VSE_CLASS)
-	    || (dump_hdr->msg_type != QCA_MEMDUMP_MSG_TYPE))
-		return false;
+restore_return:
+	skb->data = orig_data;
+	skb->len = orig_len;
+	return false;
 
-	return true;
 }
 
 static int btusb_recv_acl_qca(struct hci_dev *hdev, struct sk_buff *skb)
-- 
2.43.0