From: Nathan Chancellor nathan@kernel.org
[ Upstream commit 890d637523eec9d730e3885532fa1228ba678880 ]
With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), indirect call targets are validated against the expected function pointer prototype to make sure the call target is valid to help mitigate ROP attacks. If they are not identical, there is a failure at run time, which manifests as either a kernel panic or thread getting killed. A proposed warning in clang aims to catch these at compile time, which reveals:
drivers/gpu/drm/mediatek/mtk_hdmi.c:1407:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_bridge *, const struct drm_display_info *, const struct drm_display_mode *)' with an expression of type 'int (struct drm_bridge *, const struct drm_display_info *, const struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] .mode_valid = mtk_hdmi_bridge_mode_valid, ^~~~~~~~~~~~~~~~~~~~~~~~~~ 1 error generated.
->mode_valid() in 'struct drm_bridge_funcs' expects a return type of 'enum drm_mode_status', not 'int'. Adjust the return type of mtk_hdmi_bridge_mode_valid() to match the prototype's to resolve the warning and CFI failure.
Link: https://github.com/ClangBuiltLinux/linux/issues/1750 Reported-by: Sami Tolvanen samitolvanen@google.com Signed-off-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Kees Cook keescook@chromium.org Reviewed-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Chun-Kuang Hu chunkuang.hu@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/mediatek/mtk_hdmi.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c index 4c80b6896dc3..6e8f99554f54 100644 --- a/drivers/gpu/drm/mediatek/mtk_hdmi.c +++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c @@ -1202,9 +1202,10 @@ static enum drm_connector_status mtk_hdmi_detect(struct mtk_hdmi *hdmi) return mtk_hdmi_update_plugged_status(hdmi); }
-static int mtk_hdmi_bridge_mode_valid(struct drm_bridge *bridge, - const struct drm_display_info *info, - const struct drm_display_mode *mode) +static enum drm_mode_status +mtk_hdmi_bridge_mode_valid(struct drm_bridge *bridge, + const struct drm_display_info *info, + const struct drm_display_mode *mode) { struct mtk_hdmi *hdmi = hdmi_ctx_from_bridge(bridge); struct drm_bridge *next_bridge;