[PATCH v2] Bluetooth: SMP: add missing skb len check in smp_cmd_keypress_notify

[Muhammad Bilal <meatuni001@gmail.com>]

smp_cmd_keypress_notify() accesses the received payload as
struct smp_cmd_keypress_notify without verifying that skb->len
contains enough data.

smp_sig_channel() removes the opcode byte before dispatching to
command handlers, so a SMP_CMD_KEYPRESS_NOTIFY packet without a
payload leaves skb->len equal to zero on entry to the handler,
causing a 1-byte out-of-bounds read from the heap.

Use skb_pull_data() to safely consume the payload; it performs
a bounds check internally and returns NULL when the packet is too
short.  Add a ratelimited warning in that path to aid debugging
of malformed packets, matching the pattern used by hci_event.c.

Fixes: 1408bb6efb04 ("Bluetooth: Add dummy handler for LE SC keypress notification")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
 net/bluetooth/smp.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 98f1da4f5..1b237e623 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -2930,7 +2930,15 @@ static int smp_cmd_dhkey_check(struct l2cap_conn *conn, struct sk_buff *skb)
 static int smp_cmd_keypress_notify(struct l2cap_conn *conn,
 				   struct sk_buff *skb)
 {
-	struct smp_cmd_keypress_notify *kp = (void *) skb->data;
+	struct smp_cmd_keypress_notify *kp;
+
+	kp = skb_pull_data(skb, sizeof(struct smp_cmd_keypress_notify));
+	if (!kp) {
+		bt_dev_warn_ratelimited(conn->hcon->hdev,
+					"Too small packet: skb->len %u < %zu",
+					skb->len, sizeof(struct smp_cmd_keypress_notify));
+		return SMP_INVALID_PARAMS;
+	}
 
 	bt_dev_dbg(conn->hcon->hdev, "value 0x%02x", kp->value);
 
-- 
2.54.0