From 0fdc1a11c9cc05ea281d47235ecf9d5bee2ff505 Mon Sep 17 00:00:00 2001
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Date: Thu, 20 Apr 2023 09:32:56 +0200
Subject: [PATCH] tests: don't segfault if gpio-sim is unavailable

The GLib wrapper for libgpiosim tries to create the gpiosim context and
bank objects in the class's init() function but the constructed()
callback doesn't check if that operation succeeded, leading to a crash
when it dereferences the bank pointer.

As init() should only perform operations that cannot fail, let's move all
the gpiosim initialization code to constructed() and bail-out of it if
any of the steps fails.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 tests/gpiod-test-sim.c | 105 +++++++++++++++++++++--------------------
 1 file changed, 54 insertions(+), 51 deletions(-)

diff --git a/tests/gpiod-test-sim.c b/tests/gpiod-test-sim.c
index 161a09f..ac6c71a 100644
--- a/tests/gpiod-test-sim.c
+++ b/tests/gpiod-test-sim.c
@@ -180,11 +180,53 @@ static gboolean g_gpiosim_chip_enable(GPIOSimChip *self)
 	return TRUE;
 }
 
+static gboolean g_gpiosim_ctx_init(GError **err)
+{
+	sim_ctx = gpiosim_ctx_new();
+	if (!sim_ctx) {
+		g_set_error(err, G_GPIOSIM_ERROR,
+			    G_GPIOSIM_ERR_CTX_INIT_FAILED,
+			    "Unable to initialize libgpiosim: %s",
+			    g_strerror(errno));
+		return FALSE;
+	}
+
+	atexit(g_gpiosim_ctx_unref);
+
+	return TRUE;
+}
+
 static void g_gpiosim_chip_constructed(GObject *obj)
 {
 	GPIOSimChip *self = G_GPIOSIM_CHIP(obj);
+	struct gpiosim_dev *dev;
 	gboolean ret;
 
+	if (!sim_ctx) {
+		ret = g_gpiosim_ctx_init(&self->construct_err);
+		if (!ret)
+			return;
+	}
+
+	dev = gpiosim_dev_new(sim_ctx);
+	if (!dev) {
+		g_set_error(&self->construct_err, G_GPIOSIM_ERROR,
+			    G_GPIOSIM_ERR_CHIP_INIT_FAILED,
+			    "Unable to instantiate new GPIO device: %s",
+			    g_strerror(errno));
+		return;
+	}
+
+	self->bank = gpiosim_bank_new(dev);
+	gpiosim_dev_unref(dev);
+	if (!self->bank) {
+		g_set_error(&self->construct_err, G_GPIOSIM_ERROR,
+			    G_GPIOSIM_ERR_CHIP_INIT_FAILED,
+			    "Unable to instantiate new GPIO bank: %s",
+			    g_strerror(errno));
+		return;
+	}
+
 	ret = g_gpiosim_chip_apply_properties(self);
 	if (!ret)
 		return;
@@ -263,16 +305,12 @@ static void g_gpiosim_chip_dispose(GObject *obj)
 	G_OBJECT_CLASS(g_gpiosim_chip_parent_class)->dispose(obj);
 }
 
-static void g_gpiosim_chip_finalize(GObject *obj)
+static void g_gpiosim_disable_and_cleanup(struct gpiosim_bank *bank)
 {
-	GPIOSimChip *self = G_GPIOSIM_CHIP(obj);
 	struct gpiosim_dev *dev;
 	gint ret;
 
-	g_clear_error(&self->construct_err);
-	g_clear_pointer(&self->label, g_free);
-
-	dev = gpiosim_bank_get_dev(self->bank);
+	dev = gpiosim_bank_get_dev(bank);
 
 	if (gpiosim_dev_is_live(dev)) {
 		ret = gpiosim_dev_disable(dev);
@@ -282,7 +320,16 @@ static void g_gpiosim_chip_finalize(GObject *obj)
 	}
 
 	gpiosim_dev_unref(dev);
-	gpiosim_bank_unref(self->bank);
+	gpiosim_bank_unref(bank);
+}
+
+static void g_gpiosim_chip_finalize(GObject *obj)
+{
+	GPIOSimChip *self = G_GPIOSIM_CHIP(obj);
+
+	g_clear_error(&self->construct_err);
+	g_clear_pointer(&self->label, g_free);
+	g_clear_pointer(&self->bank, g_gpiosim_disable_and_cleanup);
 
 	G_OBJECT_CLASS(g_gpiosim_chip_parent_class)->finalize(obj);
 }
@@ -340,57 +387,13 @@ static void g_gpiosim_chip_class_init(GPIOSimChipClass *chip_class)
 			G_PARAM_WRITABLE | G_PARAM_CONSTRUCT_ONLY));
 }
 
-static gboolean g_gpiosim_ctx_init(GError **err)
-{
-	sim_ctx = gpiosim_ctx_new();
-	if (!sim_ctx) {
-		g_set_error(err, G_GPIOSIM_ERROR,
-			    G_GPIOSIM_ERR_CTX_INIT_FAILED,
-			    "Unable to initialize libgpiosim: %s",
-			    g_strerror(errno));
-		return FALSE;
-	}
-
-	atexit(g_gpiosim_ctx_unref);
-
-	return TRUE;
-}
-
 static void g_gpiosim_chip_init(GPIOSimChip *self)
 {
-	struct gpiosim_dev *dev;
-	int ret;
-
 	self->construct_err = NULL;
 	self->num_lines = 1;
 	self->label = NULL;
 	self->line_names = NULL;
 	self->hogs = NULL;
-
-	if (!sim_ctx) {
-		ret = g_gpiosim_ctx_init(&self->construct_err);
-		if (!ret)
-			return;
-	}
-
-	dev = gpiosim_dev_new(sim_ctx);
-	if (!dev) {
-		g_set_error(&self->construct_err, G_GPIOSIM_ERROR,
-			    G_GPIOSIM_ERR_CHIP_INIT_FAILED,
-			    "Unable to instantiate new GPIO device: %s",
-			    g_strerror(errno));
-		return;
-	}
-
-	self->bank = gpiosim_bank_new(dev);
-	gpiosim_dev_unref(dev);
-	if (!self->bank) {
-		g_set_error(&self->construct_err, G_GPIOSIM_ERROR,
-			    G_GPIOSIM_ERR_CHIP_INIT_FAILED,
-			    "Unable to instantiate new GPIO bank: %s",
-			    g_strerror(errno));
-		return;
-	}
 }
 
 static const gchar *
-- 
2.30.2