Check scancode before use in glfwGetKeyName

(cherry picked from commit 5f1631cb0e)

README.md

@@ -119,6 +119,8 @@ information on what to include when reporting a bug.
 ## Changelog
 
  - [Win32] Bugfix: Super key was not released after Win+V hotkey (#1622)
+ - [Win32] Bugfix: `glfwGetKeyName` could access out of bounds and return an
+   invalid pointer
  - [Cocoa] Added support for `VK_EXT_metal_surface` (#1619)
  - [Cocoa] Added locating the Vulkan loader at runtime in an application bundle
  - [X11] Bugfix: `glfwFocusWindow` could terminate on older WMs or without a WM

src/cocoa_window.m

@@ -1516,6 +1516,13 @@ const char* _glfwPlatformGetScancodeName(int scancode)
 {
     @autoreleasepool {
 
+    if (scancode < 0 || scancode > 0xff ||
+        _glfw.ns.keycodes[scancode] == GLFW_KEY_UNKNOWN)
+    {
+        _glfwInputError(GLFW_INVALID_VALUE, "Invalid scancode");
+        return NULL;
+    }
+
     const int key = _glfw.ns.keycodes[scancode];
 
     UInt32 deadKeyState = 0;

src/win32_window.c

@@ -2016,6 +2016,13 @@ void _glfwPlatformSetCursorMode(_GLFWwindow* window, int mode)
 
 const char* _glfwPlatformGetScancodeName(int scancode)
 {
+    if (scancode < 0 || scancode > (KF_EXTENDED | 0xff) ||
+        _glfw.win32.keycodes[scancode] == GLFW_KEY_UNKNOWN)
+    {
+        _glfwInputError(GLFW_INVALID_VALUE, "Invalid scancode");
+        return NULL;
+    }
+
     return _glfw.win32.keynames[_glfw.win32.keycodes[scancode]];
 }
 

src/x11_window.c

@@ -2862,6 +2862,13 @@ const char* _glfwPlatformGetScancodeName(int scancode)
     if (!_glfw.x11.xkb.available)
         return NULL;
 
+    if (scancode < 0 || scancode > 0xff ||
+        _glfw.x11.keycodes[scancode] == GLFW_KEY_UNKNOWN)
+    {
+        _glfwInputError(GLFW_INVALID_VALUE, "Invalid scancode");
+        return NULL;
+    }
+
     const int key = _glfw.x11.keycodes[scancode];
     const KeySym keysym = XkbKeycodeToKeysym(_glfw.x11.display,
                                              scancode, _glfw.x11.xkb.group, 0);