AUDIO: Fix abuse of driver IDs in OPL code.

If the driver id did not match the array index, the wrong driver entry would
be accessed causing a crash in the worst case.

2 files changed, 19 insertions, 1 deletions

diff --git a/audio/fmopl.cpp b/audio/fmopl.cpp
index 30229ea6bf..00e49ef598 100644
--- a/audio/fmopl.cpp
+++ b/audio/fmopl.cpp
@@ -63,6 +63,15 @@ Config::DriverId Config::parse(const Common::String &name) {
 	return -1;
 }
 
+const Config::EmulatorDescription *Config::findDriver(DriverId id) {
+	for (int i = 0; _drivers[i].name; ++i) {
+		if (_drivers[i].id == id)
+			return &_drivers[i];
+	}
+
+	return 0;
+}
+
 Config::DriverId Config::detect(OplType type) {
 	uint32 flags = 0;
 	switch (type) {
@@ -90,8 +99,11 @@ Config::DriverId Config::detect(OplType type) {
 	// When a valid driver is selected, check whether it supports
 	// the requested OPL chip.
 	if (drv != -1 && drv != kAuto) {
+		const EmulatorDescription *driverDesc = findDriver(drv);
 		// If the chip is supported, just use the driver.
-		if ((flags & _drivers[drv].flags)) {
+		if (!driverDesc) {
+			warning("The selected OPL driver %d could not be found", drv);
+		} else if ((flags & driverDesc->flags)) {
 			return drv;
 		} else {
 			// Else we will output a warning and just
diff --git a/audio/fmopl.h b/audio/fmopl.h
index 85ac606c7a..28dd456e21 100644
--- a/audio/fmopl.h
+++ b/audio/fmopl.h
@@ -71,6 +71,12 @@ public:
 	static DriverId parse(const Common::String &name);
 
 	/**
+	 * @return The driver description for the given id or 0 in case it is not
+	 *         available.
+	 */
+	static const EmulatorDescription *findDriver(DriverId id);
+
+	/**
 	 * Detects a driver for the specific type.
 	 *
 	 * @return Returns a valid driver id on success, -1 otherwise.