examples: Fix use after free and resource leaks

The emulator example plugin does not track modem powered watches, and
thus leaks them.  Additionally, the plugin opens ports for both HFP and
DUN emulators.  However, only a single server watch is tracked, leading
to the other watch being leaked.

Since the modem powered watches are not tracked, they are never
unregistered.  This can lead to situations where emulator plugin is
destroyed (and thus all data associated with it is freed) before all
modems have been removed.  When modems are removed subsequently,
registered powered watches will be invoked.  This will result in
use-after-free errors being reported by valgrind.

1 files changed, 108 insertions, 43 deletions

diff --git a/examples/emulator.c b/examples/emulator.c
index 5c92bd665..927cf1fa8 100644
--- a/examples/emulator.c
+++ b/examples/emulator.c
@@ -44,8 +44,48 @@
 #define HFP_PORT 12347
 
 static unsigned int modemwatch_id;
-guint server_watch;
-static GList *modems;
+static guint dun_watch;
+static guint hfp_watch;
+static struct l_queue *modem_infos;
+static unsigned int n_powered;
+
+struct modem_info {
+	struct ofono_modem *modem;
+	unsigned int watch_id;
+};
+
+static bool modem_matches(const void *data, const void *user_data)
+{
+	const struct modem_info *info = data;
+
+	return info->modem == user_data;
+}
+
+static void modem_info_free(struct modem_info *info)
+{
+	if (!info)
+		return;
+
+	if (info->watch_id)
+		__ofono_modem_remove_powered_watch(info->modem, info->watch_id);
+
+	l_free(info);
+}
+
+static struct ofono_modem *find_first_powered(void)
+{
+	const struct l_queue_entry *entry;
+
+	for (entry = l_queue_get_entries(modem_infos); entry;
+							entry = entry->next) {
+		struct ofono_modem *modem = entry->data;
+
+		if (ofono_modem_get_powered(modem))
+			return modem;
+	}
+
+	return NULL;
+}
 
 static gboolean on_socket_connected(GIOChannel *chan, GIOCondition cond,
 							gpointer user)
@@ -64,28 +104,35 @@ static gboolean on_socket_connected(GIOChannel *chan, GIOCondition cond,
 		return FALSE;
 
 	/* Pick the first powered modem */
-	modem = modems->data;
+	modem = find_first_powered();
+	if (!modem)
+		goto error;
+
 	DBG("Picked modem %p for emulator", modem);
 
 	em = ofono_emulator_create(modem, GPOINTER_TO_INT(user));
-	if (em == NULL)
-		close(fd);
-	else
-		ofono_emulator_register(em, fd);
+	if (!em)
+		goto error;
+
+	ofono_emulator_register(em, fd);
+	return TRUE;
 
+error:
+	close(fd);
 	return TRUE;
 }
 
-static gboolean create_tcp(short port, enum ofono_emulator_type type)
+static guint create_tcp(short port, enum ofono_emulator_type type)
 {
 	struct sockaddr_in addr;
 	int sk;
 	int reuseaddr = 1;
 	GIOChannel *server;
+	guint server_watch;
 
 	sk = socket(PF_INET, SOCK_STREAM, 0);
 	if (sk < 0)
-		return FALSE;
+		return 0;
 
 	memset(&addr, 0, sizeof(addr));
 
@@ -108,62 +155,77 @@ static gboolean create_tcp(short port, enum ofono_emulator_type type)
 				G_IO_IN | G_IO_HUP | G_IO_ERR | G_IO_NVAL,
 				on_socket_connected, GINT_TO_POINTER(type),
 				NULL);
-
 	g_io_channel_unref(server);
 
 	DBG("Created server_watch: %u", server_watch);
-
-	return TRUE;
+	return server_watch;
 
 err:
 	close(sk);
-	return FALSE;
+	return 0;
+}
+
+static void powered_watch_destroy(void *user)
+{
+	struct modem_info *info = user;
+
+	DBG("");
+
+	info->watch_id = 0;
 }
 
 static void powered_watch(struct ofono_modem *modem, gboolean powered,
 				void *user)
 {
+	DBG("powered: %d", powered);
+
 	if (powered == FALSE) {
-		DBG("Removing modem %p from the list", modem);
-		modems = g_list_remove(modems, modem);
-
-		if (modems == NULL && server_watch > 0) {
-			DBG("Removing server watch: %u", server_watch);
-			g_source_remove(server_watch);
-			server_watch = 0;
-		}
-	} else {
-		DBG("Adding modem %p to the list", modem);
-		modems = g_list_append(modems, modem);
-
-		if (modems->next == NULL) {
-			create_tcp(DUN_PORT, OFONO_EMULATOR_TYPE_DUN);
-			create_tcp(HFP_PORT, OFONO_EMULATOR_TYPE_HFP);
-		}
+		n_powered -= 1;
+
+		if (n_powered)
+			return;
+
+		g_source_remove(dun_watch);
+		dun_watch = 0;
+
+		g_source_remove(hfp_watch);
+		hfp_watch = 0;
+
+		return;
 	}
+
+	n_powered += 1;
+
+	if (!dun_watch)
+		dun_watch = create_tcp(DUN_PORT, OFONO_EMULATOR_TYPE_DUN);
+
+	if (!hfp_watch)
+		hfp_watch = create_tcp(HFP_PORT, OFONO_EMULATOR_TYPE_HFP);
 }
 
 static void modem_watch(struct ofono_modem *modem, gboolean added, void *user)
 {
+	struct modem_info *info;
+
 	DBG("modem: %p, added: %d", modem, added);
 
 	if (added == FALSE) {
-		DBG("Removing modem %p from the list", modem);
-		modems = g_list_remove(modems, modem);
+		info = l_queue_remove_if(modem_infos, modem_matches, modem);
+		DBG("Removing modem %p, info %p, from the list", modem, info);
+		modem_info_free(info);
 		return;
 	}
 
-	if (ofono_modem_get_powered(modem) == TRUE) {
-		DBG("Adding modem %p to the list", modem);
-		modems = g_list_append(modems, modem);
+	info = l_new(struct modem_info, 1);
+	info->modem = modem;
+	info->watch_id = __ofono_modem_add_powered_watch(modem, powered_watch,
+							info,
+							powered_watch_destroy);
 
-		if (modems->next == NULL) {
-			create_tcp(DUN_PORT, OFONO_EMULATOR_TYPE_DUN);
-			create_tcp(HFP_PORT, OFONO_EMULATOR_TYPE_HFP);
-		}
-	}
+	l_queue_push_tail(modem_infos, info);
 
-	__ofono_modem_add_powered_watch(modem, powered_watch, NULL, NULL);
+	if (ofono_modem_get_powered(modem) == TRUE)
+		powered_watch(modem, TRUE, NULL);
 }
 
 static void call_modemwatch(struct ofono_modem *modem, void *user)
@@ -175,6 +237,7 @@ static int example_emulator_init(void)
 {
 	DBG("");
 
+	modem_infos = l_queue_new();
 	modemwatch_id = __ofono_modemwatch_add(modem_watch, NULL, NULL);
 
 	__ofono_modem_foreach(call_modemwatch, NULL);
@@ -187,11 +250,13 @@ static void example_emulator_exit(void)
 	DBG("");
 
 	__ofono_modemwatch_remove(modemwatch_id);
+	l_queue_destroy(modem_infos, (l_queue_destroy_func_t) modem_info_free);
 
-	g_list_free(modems);
+	if (dun_watch)
+		g_source_remove(dun_watch);
 
-	if (server_watch)
-		g_source_remove(server_watch);
+	if (hfp_watch)
+		g_source_remove(hfp_watch);
 }
 
 OFONO_PLUGIN_DEFINE(example_emulator, "Example AT Modem Emulator Plugin",