Commit e4ef1885d91eab727f5c59b6b173c2ae1e8540d3
2017-10-16T14:57:42
Fixed bug 3890 - Incomplete fix for CVE-2017-2888 Felix Geyer http://hg.libsdl.org/SDL/rev/a31ee4d64ff6 tries to fix CVE-2017-2888. Unfortunately compilers may optimize the second condition "(size / surface->pitch) != surface->h" away. See https://bugzilla.redhat.com/show_bug.cgi?id=1500623#c2 I've verified that this is also the case on Debian unstable (gcc 7.2).
diff --git a/src/video/SDL_surface.c b/src/video/SDL_surface.c
index 2c64291..38addea 100644
--- a/src/video/SDL_surface.c
+++ b/src/video/SDL_surface.c
@@ -37,6 +37,10 @@ SDL_ConvertPixels_ARGB8888_to_YUV(int width, int height,
const void *src, int src_pitch,
Uint32 dst_format, void *dst);
+/* Check to make sure we can safely check multiplication of surface w and pitch and it won't overflow size_t */
+SDL_COMPILE_TIME_ASSERT(surface_size_assumptions,
+ sizeof(int) == sizeof(Sint32) && sizeof(size_t) >= sizeof(Sint32));
+
/* Public routines */
/*
@@ -91,15 +95,16 @@ SDL_CreateRGBSurfaceWithFormat(Uint32 flags, int width, int height, int depth,
/* Get the pixels */
if (surface->w && surface->h) {
- int size = (surface->h * surface->pitch);
- if (size < 0 || (size / surface->pitch) != surface->h) {
+ /* Assumptions checked in surface_size_assumptions assert above */
+ Sint64 size = ((Sint64)surface->h * surface->pitch);
+ if (size < 0 || size > SDL_MAX_SINT32) {
/* Overflow... */
SDL_FreeSurface(surface);
SDL_OutOfMemory();
return NULL;
}
- surface->pixels = SDL_malloc(size);
+ surface->pixels = SDL_malloc((size_t)size);
if (!surface->pixels) {
SDL_FreeSurface(surface);
SDL_OutOfMemory();