AK: Add trivial structure validation to SharedBuffer

If we're sharing buffers, we only want to share trivial structures
as anything else could potentially share internal pointers, which
most likely is going to cause problems due to different address
spaces.

Fix the GUI::SystemTheme structure, which was not trivial, which
is now caught at compile time.

Fixes #3650

Libraries/LibGfx/Bitmap.cpp

@@ -169,7 +169,7 @@ RefPtr<Bitmap> Bitmap::create_with_shared_buffer(BitmapFormat format, NonnullRef
 
 Bitmap::Bitmap(BitmapFormat format, NonnullRefPtr<SharedBuffer>&& shared_buffer, const IntSize& size, const Vector<RGBA32>& palette)
     : m_size(size)
-    , m_data(shared_buffer->data())
+    , m_data(shared_buffer->data<void>())
     , m_pitch(minimum_pitch(size.width(), format))
     , m_format(format)
     , m_shared_buffer(move(shared_buffer))
@@ -255,7 +255,7 @@ RefPtr<Bitmap> Bitmap::to_bitmap_backed_by_shared_buffer() const
     auto bitmap = Bitmap::create_with_shared_buffer(m_format, *buffer, m_size, palette_to_vector());
     if (!bitmap)
         return nullptr;
-    memcpy(buffer->data(), scanline(0), size_in_bytes());
+    memcpy(buffer->data<void>(), scanline(0), size_in_bytes());
     return bitmap;
 }
 

Libraries/LibGfx/Palette.cpp

@@ -52,13 +52,13 @@ Palette::~Palette()
 
 const SystemTheme& PaletteImpl::theme() const
 {
-    return *(const SystemTheme*)m_theme_buffer->data();
+    return *m_theme_buffer->data<SystemTheme>();
 }
 
 Color PaletteImpl::color(ColorRole role) const
 {
     ASSERT((int)role < (int)ColorRole::__Count);
-    return theme().color[(int)role];
+    return Color::from_rgba(theme().color[(int)role]);
 }
 
 int PaletteImpl::metric(MetricRole role) const
@@ -76,7 +76,7 @@ String PaletteImpl::path(PathRole role) const
 NonnullRefPtr<PaletteImpl> PaletteImpl::clone() const
 {
     auto new_theme_buffer = SharedBuffer::create_with_size(m_theme_buffer->size());
-    memcpy(new_theme_buffer->data(), m_theme_buffer->data(), m_theme_buffer->size());
+    memcpy(new_theme_buffer->data<SystemTheme>(), &theme(), m_theme_buffer->size());
     return adopt(*new PaletteImpl(*new_theme_buffer));
 }
 
@@ -85,7 +85,7 @@ void Palette::set_color(ColorRole role, Color color)
     if (m_impl->ref_count() != 1)
         m_impl = m_impl->clone();
     auto& theme = const_cast<SystemTheme&>(impl().theme());
-    theme.color[(int)role] = color;
+    theme.color[(int)role] = color.value();
 }
 
 void Palette::set_metric(MetricRole role, int value)
@@ -101,7 +101,8 @@ void Palette::set_path(PathRole role, String path)
     if (m_impl->ref_count() != 1)
         m_impl = m_impl->clone();
     auto& theme = const_cast<SystemTheme&>(impl().theme());
-    theme.path[(int)role] = path;
+    memcpy(theme.path[(int)role], path.characters(), min(path.length() + 1, sizeof(theme.path[(int)role])));
+    theme.path[(int)role][sizeof(theme.path[(int)role]) - 1] = '\0';
 }
 
 PaletteImpl::~PaletteImpl()

Libraries/LibGfx/SystemTheme.cpp

@@ -27,6 +27,7 @@
 #include <AK/SharedBuffer.h>
 #include <LibCore/ConfigFile.h>
 #include <LibGfx/SystemTheme.h>
+#include <string.h>
 
 namespace Gfx {
 
@@ -49,7 +50,7 @@ int current_system_theme_buffer_id()
 void set_system_theme(SharedBuffer& buffer)
 {
     theme_buffer = buffer;
-    theme_page = (SystemTheme*)theme_buffer->data();
+    theme_page = theme_buffer->data<SystemTheme>();
 }
 
 RefPtr<SharedBuffer> load_system_theme(const String& path)
@@ -57,7 +58,7 @@ RefPtr<SharedBuffer> load_system_theme(const String& path)
     auto file = Core::ConfigFile::open(path);
     auto buffer = SharedBuffer::create_with_size(sizeof(SystemTheme));
 
-    auto* data = (SystemTheme*)buffer->data();
+    auto* data = buffer->data<SystemTheme>();
 
     auto get_color = [&](auto& name) {
         auto color_string = file->read_entry("Colors", name);
@@ -100,7 +101,7 @@ RefPtr<SharedBuffer> load_system_theme(const String& path)
 
 #undef __ENUMERATE_COLOR_ROLE
 #define __ENUMERATE_COLOR_ROLE(role) \
-    data->color[(int)ColorRole::role] = get_color(#role);
+    data->color[(int)ColorRole::role] = get_color(#role).value();
     ENUMERATE_COLOR_ROLES(__ENUMERATE_COLOR_ROLE)
 #undef __ENUMERATE_COLOR_ROLE
 
@@ -111,8 +112,12 @@ RefPtr<SharedBuffer> load_system_theme(const String& path)
     DO_METRIC(TitleButtonWidth);
     DO_METRIC(TitleButtonHeight);
 
-#define DO_PATH(x) \
-    data->path[(int)PathRole::x] = get_path(#x, (int)PathRole::x)
+#define DO_PATH(x)                                                                                               \
+    do {                                                                                                         \
+        auto path = get_path(#x, (int)PathRole::x);                                                              \
+        memcpy(data->path[(int)PathRole::x], path, min(strlen(path) + 1, sizeof(data->path[(int)PathRole::x]))); \
+        data->path[(int)PathRole::x][sizeof(data->path[(int)PathRole::x]) - 1] = '\0';                           \
+    } while (0)
 
     DO_PATH(TitleButtonIcons);
 

Libraries/LibGfx/SystemTheme.h

@@ -143,9 +143,9 @@ enum class PathRole {
 };
 
 struct SystemTheme {
-    Color color[(int)ColorRole::__Count];
+    RGBA32 color[(int)ColorRole::__Count];
     int metric[(int)MetricRole::__Count];
-    String path[(int)PathRole::__Count];
+    char path[(int)PathRole::__Count][256]; // TODO: PATH_MAX?
 };
 
 const SystemTheme& current_system_theme();