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syswm: prevent buffer overflow if SDL and app have different config headers.

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This only affects Wayland and DirectFB, as a Unix system generally has X11
support. Other platforms also have different sizes for the C union in
question, but are likely the only target for that platform, etc.

Apps that might run on Wayland or DirectFB will need to be compiled against
new headers from an official 2.0.6 release, or be prepared to force the x11
target, or not use SDL_GetWindowWMInfo().

Fixes Bugzilla #3428.
This commit is contained in:
Ryan C. Gordon
2017-06-11 00:50:26 -04:00
parent 43d62b7459
commit 3c955d0540
3 changed files with 40 additions and 2 deletions
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18
src/video/wayland/SDL_waylandwindow.c
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@@ -129,6 +129,24 @@ SDL_bool
Wayland_GetWindowWMInfo(_THIS, SDL_Window * window, SDL_SysWMinfo * info)
{
SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
const Uint32 version = ((((Uint32) info->version.major) * 1000000) +
(((Uint32) info->version.minor) * 10000) +
(((Uint32) info->version.patch)));
/* Before 2.0.6, it was possible to build an SDL with Wayland support
(SDL_SysWMinfo will be large enough to hold Wayland info), but build
your app against SDL headers that didn't have Wayland support
(SDL_SysWMinfo could be smaller than Wayland needs. This would lead
to an app properly using SDL_GetWindowWMInfo() but we'd accidentally
overflow memory on the stack or heap. To protect against this, we've
padded out the struct unconditionally in the headers and Wayland will
just return an error for older apps using this function. Those apps
will need to be recompiled against newer headers or not use Wayland,
maybe by forcing SDL_VIDEODRIVER=x11. */
if (version < 2000006) {
info->subsystem = SDL_SYSWM_UNKNOWN;
return SDL_FALSE;
}
info->info.wl.display = data->waylandData->display;
info->info.wl.surface = data->surface;