Bluetooth: MGMT: fix crash in set_mesh_sync and set_mesh_complete

There is a BUG: KASAN: stack-out-of-bounds in set_mesh_sync due to
memcpy from badly declared on-stack flexible array.

Another crash is in set_mesh_complete() due to double list_del via
mgmt_pending_valid + mgmt_pending_remove.

Use DEFINE_FLEX to declare the flexible array right, and don't memcpy
outside bounds.

As mgmt_pending_valid removes the cmd from list, use mgmt_pending_free,
and also report status on error.

Fixes: 302a1f674c00d ("Bluetooth: MGMT: Fix possible UAFs")
Signed-off-by: Pauli Virtanen <[e-mail]>
Reviewed-by: Paul Menzel <[e-mail]>
Signed-off-by: Luiz Augusto von Dentz <[e-mail]>

include/net/bluetooth/mgmt.h

···
 	__le16 window;
 	__le16 period;
 	__u8   num_ad_types;
-	__u8   ad_types[];
+	__u8   ad_types[] __counted_by(num_ad_types);
 } __packed;
 #define MGMT_SET_MESH_RECEIVER_SIZE	6
 

net/bluetooth/mgmt.c

···
 	sk = cmd->sk;
 
 	if (status) {
+		mgmt_cmd_status(cmd->sk, hdev->id, MGMT_OP_SET_MESH_RECEIVER,
+				status);
 		mgmt_pending_foreach(MGMT_OP_SET_MESH_RECEIVER, hdev, true,
 				     cmd_status_rsp, &status);
-		return;
+		goto done;
 	}
 
-	mgmt_pending_remove(cmd);
 	mgmt_cmd_complete(sk, hdev->id, MGMT_OP_SET_MESH_RECEIVER, 0, NULL, 0);
+
+done:
+	mgmt_pending_free(cmd);
 }
 
 static int set_mesh_sync(struct hci_dev *hdev, void *data)
 {
 	struct mgmt_pending_cmd *cmd = data;
-	struct mgmt_cp_set_mesh cp;
+	DEFINE_FLEX(struct mgmt_cp_set_mesh, cp, ad_types, num_ad_types,
+		    sizeof(hdev->mesh_ad_types));
 	size_t len;
 
 	mutex_lock(&hdev->mgmt_pending_lock);
···
 		return -ECANCELED;
 	}
 
-	memcpy(&cp, cmd->param, sizeof(cp));
+	len = cmd->param_len;
+	memcpy(cp, cmd->param, min(__struct_size(cp), len));
 
 	mutex_unlock(&hdev->mgmt_pending_lock);
 
-	len = cmd->param_len;
-
 	memset(hdev->mesh_ad_types, 0, sizeof(hdev->mesh_ad_types));
 
-	if (cp.enable)
+	if (cp->enable)
 		hci_dev_set_flag(hdev, HCI_MESH);
 	else
 		hci_dev_clear_flag(hdev, HCI_MESH);
 
-	hdev->le_scan_interval = __le16_to_cpu(cp.period);
-	hdev->le_scan_window = __le16_to_cpu(cp.window);
+	hdev->le_scan_interval = __le16_to_cpu(cp->period);
+	hdev->le_scan_window = __le16_to_cpu(cp->window);
 
-	len -= sizeof(cp);
+	len -= sizeof(struct mgmt_cp_set_mesh);
 
 	/* If filters don't fit, forward all adv pkts */
 	if (len <= sizeof(hdev->mesh_ad_types))
-		memcpy(hdev->mesh_ad_types, cp.ad_types, len);
+		memcpy(hdev->mesh_ad_types, cp->ad_types, len);
 
 	hci_update_passive_scan_sync(hdev);
 	return 0;