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subsurface: Avoid invalid accesses

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Whenever subsurface extents are not contained in the target extents,
using the source image given by the target (with origin corrected by
using an appropriate offset in the data pointer) is not a valid
operation. Fallback to cloning in that case.
This commit is contained in:
Andrea Canciani 2010-08-26 14:24:17 +02:00
parent df4465bdd1
commit 72644c6df2
1 changed files with 11 additions and 1 deletions
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12
src/cairo-surface-subsurface.c
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@ -281,11 +281,13 @@ _cairo_surface_subsurface_acquire_source_image (void *abstrac
cairo_image_surface_t **image_out,
void **extra_out)
{
cairo_rectangle_int_t target_extents;
cairo_surface_subsurface_t *surface = abstract_surface;
cairo_image_surface_t *image;
cairo_status_t status;
struct extra *extra;
uint8_t *data;
cairo_bool_t ret;
if (surface->target->type == CAIRO_SURFACE_TYPE_RECORDING) {
cairo_recording_surface_t *meta = (cairo_recording_surface_t *) surface->target;
@ -335,8 +337,16 @@ _cairo_surface_subsurface_acquire_source_image (void *abstrac
if (unlikely (status))
goto CLEANUP;
ret = _cairo_surface_get_extents (extra->image_extra, &target_extents);
assert (ret);
/* only copy if we need to perform sub-byte manipulation */
if (PIXMAN_FORMAT_BPP (extra->image->pixman_format) >= 8) {
if (PIXMAN_FORMAT_BPP (extra->image->pixman_format) >= 8 ||
surface->extents.x < target_extents.x ||
surface->extents.y < target_extents.y ||
surface->extents.x + surface->extents.width > target_extents.x + target_extents.width ||
surface->extents.y + surface->extents.height > target_extents.y + target_extents.height) {
assert ((PIXMAN_FORMAT_BPP (extra->image->pixman_format) % 8) == 0);
data = extra->image->data + surface->extents.y * extra->image->stride;