In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Maxime Ripard <mripard@xxxxxxxxxx> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> Cc: David Airlie <airlied@xxxxxxxxx> Cc: Daniel Vetter <daniel@xxxxxxxx> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- drivers/gpu/drm/vc4/vc4_validate.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/vc4/vc4_validate.c b/drivers/gpu/drm/vc4/vc4_validate.c index 9affba9c58b3..677d9975f888 100644 --- a/drivers/gpu/drm/vc4/vc4_validate.c +++ b/drivers/gpu/drm/vc4/vc4_validate.c @@ -206,7 +206,7 @@ vc4_check_tex_size(struct vc4_exec_info *exec, struct drm_gem_dma_object *fbo, stride = aligned_width * cpp; size = stride * aligned_height; - if (size + offset < size || + if (add_would_overflow(size, offset) || size + offset > fbo->base.size) { DRM_DEBUG("Overflow in %dx%d (%dx%d) fbo size (%d + %d > %zd)\n", width, height, -- 2.34.1
