[PATCH v3] nfc: hci: fix out-of-bounds read in HCP header parsing

[Ashutosh Desai <ashutoshdesai993@gmail.com>]

nfc_hci_recv_from_llc() and nci_hci_data_received_cb() cast skb->data
to struct hcp_packet and read the message header byte without checking
that enough data is present in the linear sk_buff area. A malicious NFC
peer can send a 1-byte HCP frame that passes through the SHDLC layer
and reaches these functions, causing an out-of-bounds heap read.

Fix this by adding pskb_may_pull() before each cast to ensure the full
2-byte HCP header is pulled into the linear area before it is accessed.

Signed-off-by: Ashutosh Desai <ashutoshdesai993@gmail.com>
---
v3: drop redundant pskb_may_pull checks from msg_rx_work functions,
    remove incorrect Suggested-by tag
v2: switch skb->len check to pskb_may_pull

 net/nfc/hci/core.c | 5 +++++
 net/nfc/nci/hci.c  | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/net/nfc/hci/core.c b/net/nfc/hci/core.c
index 0d33c81a1..cd9cf6c94 100644
--- a/net/nfc/hci/core.c
+++ b/net/nfc/hci/core.c
@@ -904,6 +904,11 @@ static void nfc_hci_recv_from_llc(struct nfc_hci_dev *hdev, struct sk_buff *skb)
 	 * unblock waiting cmd context. Otherwise, enqueue to dispatch
 	 * in separate context where handler can also execute command.
 	 */
+	if (!pskb_may_pull(hcp_skb, NFC_HCI_HCP_HEADER_LEN)) {
+		kfree_skb(hcp_skb);
+		return;
+	}
+
 	packet = (struct hcp_packet *)hcp_skb->data;
 	type = HCP_MSG_GET_TYPE(packet->message.header);
 	if (type == NFC_HCI_HCP_RESPONSE) {
diff --git a/net/nfc/nci/hci.c b/net/nfc/nci/hci.c
index 40ae8e5a7..6e633da25 100644
--- a/net/nfc/nci/hci.c
+++ b/net/nfc/nci/hci.c
@@ -482,6 +482,11 @@ void nci_hci_data_received_cb(void *context,
 	 * unblock waiting cmd context. Otherwise, enqueue to dispatch
 	 * in separate context where handler can also execute command.
 	 */
+	if (!pskb_may_pull(hcp_skb, NCI_HCI_HCP_HEADER_LEN)) {
+		kfree_skb(hcp_skb);
+		return;
+	}
+
 	packet = (struct nci_hcp_packet *)hcp_skb->data;
 	type = NCI_HCP_MSG_GET_TYPE(packet->message.header);
 	if (type == NCI_HCI_HCP_RESPONSE) {
-- 
2.34.1