From b2ad4e6b24ed0271ca76cb27856def0a701fb778 Mon Sep 17 00:00:00 2001
Message-Id: <b2ad4e6b24ed0271ca76cb27856def0a701fb778.1572271835.git.davide.caratti@gmail.com>
From: Davide Caratti <davide.caratti@gmail.com>
Date: Wed, 2 Oct 2019 14:08:41 +0200
Subject: [PATCH] D-Bus: Fix P2P NULL dereference after interface removal

When the P2P management interface is deleted, P2P is then disabled and
global->p2p_init_wpa_s is set to NULL. After that, other interfaces can
still trigger P2P functions (like wpas_p2p_find()) using D-Bus. This
makes wpa_supplicant terminate with SIGSEGV, because it dereferences a
NULL pointer. Fix this by adding proper checks, like it's done with
wpa_cli.

CC: Beniamino Galvani <bgalvani@redhat.com>
CC: Benjamin Berg <benjamin@sipsolutions.net>
Reported-by: Vladimir Benes <vbenes@redhat.com>
Signed-off-by: Davide Caratti <davide.caratti@gmail.com>
---
 wpa_supplicant/dbus/dbus_new_handlers_p2p.c | 69 ++++++++++++++++++++-
 1 file changed, 67 insertions(+), 2 deletions(-)

diff --git a/wpa_supplicant/dbus/dbus_new_handlers_p2p.c b/wpa_supplicant/dbus/dbus_new_handlers_p2p.c
index 8cdd88564..19715eb4c 100644
--- a/wpa_supplicant/dbus/dbus_new_handlers_p2p.c
+++ b/wpa_supplicant/dbus/dbus_new_handlers_p2p.c
@@ -40,6 +40,14 @@ static int wpas_dbus_validate_dbus_ipaddr(struct wpa_dbus_dict_entry entry)
 }
 
 
+static dbus_bool_t no_p2p_mgmt_interface(DBusError *error)
+{
+	dbus_set_error_const(error, WPAS_DBUS_ERROR_IFACE_UNKNOWN,
+			     "Could not find P2P mgmt interface");
+	return FALSE;
+}
+
+
 /**
  * Parses out the mac address from the peer object path.
  * @peer_path - object path of the form
@@ -78,6 +86,22 @@ wpas_dbus_error_persistent_group_unknown(DBusMessage *message)
 }
 
 
+/**
+ * wpas_dbus_error_no_p2p_mgmt_iface - Return a new InterfaceUnknown error
+ * message
+ * @message: Pointer to incoming dbus message this error refers to
+ * Returns: a dbus error message
+ *
+ * Convenience function to create and return an unknown interface error.
+ */
+static DBusMessage * wpas_dbus_error_no_p2p_mgmt_iface(DBusMessage *message)
+{
+	wpa_printf(MSG_DEBUG, "dbus: Could not find P2P mgmt interface");
+	return dbus_message_new_error(message, WPAS_DBUS_ERROR_IFACE_UNKNOWN,
+				      "Could not find P2P mgmt interface");
+}
+
+
 DBusMessage * wpas_dbus_handler_p2p_find(DBusMessage *message,
 					 struct wpa_supplicant *wpa_s)
 {
@@ -145,6 +169,10 @@ DBusMessage * wpas_dbus_handler_p2p_find(DBusMessage *message,
 	}
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s) {
+		reply = wpas_dbus_error_no_p2p_mgmt_iface(message);
+		goto error_nop2p;
+	}
 
 	if (wpas_p2p_find(wpa_s, timeout, type, num_req_dev_types,
 			  req_dev_types, NULL, 0, 0, NULL, freq))
@@ -157,8 +185,9 @@ DBusMessage * wpas_dbus_handler_p2p_find(DBusMessage *message,
 error_clear:
 	wpa_dbus_dict_entry_clear(&entry);
 error:
-	os_free(req_dev_types);
 	reply = wpas_dbus_error_invalid_args(message, entry.key);
+error_nop2p:
+	os_free(req_dev_types);
 	return reply;
 }
 
@@ -166,7 +195,9 @@ error:
 DBusMessage * wpas_dbus_handler_p2p_stop_find(DBusMessage *message,
 					      struct wpa_supplicant *wpa_s)
 {
-	wpas_p2p_stop_find(wpa_s->global->p2p_init_wpa_s);
+	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (wpa_s)
+		wpas_p2p_stop_find(wpa_s);
 	return NULL;
 }
 
@@ -185,6 +216,8 @@ DBusMessage * wpas_dbus_handler_p2p_rejectpeer(DBusMessage *message,
 		return wpas_dbus_error_invalid_args(message, NULL);
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s)
+		return wpas_dbus_error_no_p2p_mgmt_iface(message);
 
 	if (wpas_p2p_reject(wpa_s, peer_addr) < 0)
 		return wpas_dbus_error_unknown_error(message,
@@ -204,6 +237,8 @@ DBusMessage * wpas_dbus_handler_p2p_listen(DBusMessage *message,
 		return wpas_dbus_error_no_memory(message);
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s)
+		return wpas_dbus_error_no_p2p_mgmt_iface(message);
 
 	if (wpas_p2p_listen(wpa_s, (unsigned int) timeout)) {
 		return dbus_message_new_error(message,
@@ -245,6 +280,8 @@ DBusMessage * wpas_dbus_handler_p2p_extendedlisten(
 	}
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s)
+		return wpas_dbus_error_no_p2p_mgmt_iface(message);
 
 	if (wpas_p2p_ext_listen(wpa_s, period, interval))
 		return wpas_dbus_error_unknown_error(
@@ -350,6 +387,10 @@ DBusMessage * wpas_dbus_handler_p2p_group_add(DBusMessage *message,
 	}
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s) {
+		reply = wpas_dbus_error_no_p2p_mgmt_iface(message);
+		goto out;
+	}
 
 	if (pg_object_path != NULL) {
 		char *net_id_str;
@@ -433,6 +474,12 @@ static dbus_bool_t wpa_dbus_p2p_check_enabled(struct wpa_supplicant *wpa_s,
 				     "P2P is not available for this interface");
 		return FALSE;
 	}
+	if (!wpa_s->global->p2p_init_wpa_s) {
+		if (out_reply)
+			*out_reply = wpas_dbus_error_no_p2p_mgmt_iface(
+				message);
+		return no_p2p_mgmt_interface(error);
+	}
 	return TRUE;
 }
 
@@ -822,6 +869,8 @@ DBusMessage * wpas_dbus_handler_p2p_prov_disc_req(DBusMessage *message,
 		return wpas_dbus_error_invalid_args(message, NULL);
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s)
+		return wpas_dbus_error_no_p2p_mgmt_iface(message);
 
 	if (wpas_p2p_prov_disc(wpa_s, peer_addr, config_method,
 			       WPAS_P2P_PD_FOR_GO_NEG, NULL) < 0)
@@ -1882,6 +1931,8 @@ dbus_bool_t wpas_dbus_getter_p2p_peer_groups(
 
 	wpa_s = peer_args->wpa_s;
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s)
+		return no_p2p_mgmt_interface(error);
 
 	wpa_s_go = wpas_get_p2p_client_iface(wpa_s, info->p2p_device_addr);
 	if (wpa_s_go) {
@@ -1963,6 +2014,9 @@ dbus_bool_t wpas_dbus_getter_persistent_groups(
 	dbus_bool_t success = FALSE;
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s)
+		return no_p2p_mgmt_interface(error);
+
 	if (!wpa_s->parent->dbus_new_path)
 		return FALSE;
 
@@ -2077,6 +2131,11 @@ DBusMessage * wpas_dbus_handler_add_persistent_group(
 	dbus_message_iter_init(message, &iter);
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s) {
+		reply = wpas_dbus_error_no_p2p_mgmt_iface(message);
+		goto err;
+	}
+
 	if (wpa_s->parent->dbus_new_path)
 		ssid = wpa_config_add_network(wpa_s->conf);
 	if (ssid == NULL) {
@@ -2159,6 +2218,10 @@ DBusMessage * wpas_dbus_handler_remove_persistent_group(
 			      DBUS_TYPE_INVALID);
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s) {
+		reply = wpas_dbus_error_no_p2p_mgmt_iface(message);
+		goto out;
+	}
 
 	/*
 	 * Extract the network ID and ensure the network is actually a child of
@@ -2235,6 +2298,8 @@ DBusMessage * wpas_dbus_handler_remove_all_persistent_groups(
 	struct wpa_config *config;
 
 	wpa_s = wpa_s->global->p2p_init_wpa_s;
+	if (!wpa_s)
+		return wpas_dbus_error_no_p2p_mgmt_iface(message);
 
 	config = wpa_s->conf;
 	ssid = config->ssid;
-- 
2.21.0