Messages in this thread | | | Date | Wed, 2 Nov 2022 12:06:50 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] drm/sti: Fix return type of sti_{dvo,hda,hdmi}_connector_mode_valid() |
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On Wed, Nov 02, 2022 at 08:56:23AM -0700, Nathan Chancellor wrote: > 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/sti/sti_hda.c:637:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] > .mode_valid = sti_hda_connector_mode_valid, > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > drivers/gpu/drm/sti/sti_dvo.c:376:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] > .mode_valid = sti_dvo_connector_mode_valid, > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > drivers/gpu/drm/sti/sti_hdmi.c:1035:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] > .mode_valid = sti_hdmi_connector_mode_valid, > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > ->mode_valid() in 'struct drm_connector_helper_funcs' expects a return > type of 'enum drm_mode_status', not 'int'. Adjust the return type of > sti_{dvo,hda,hdmi}_connector_mode_valid() to match the prototype's to > resolve the warning and CFI failure. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1750 > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
-- Kees Cook
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