On Mon, Nov 14, 2022 at 03:03:05PM -0700, Nathan Chancellor wrote: > Hi all, > > On Wed, Nov 02, 2022 at 08:42:15AM -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/fsl-dcu/fsl_dcu_drm_rgb.c:74:16: 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 = fsl_dcu_drm_connector_mode_valid, > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > 1 error generated. > > > > ->mode_valid() in 'struct drm_connector_helper_funcs' expects a return > > type of 'enum drm_mode_status', not 'int'. Adjust the return type of > > fsl_dcu_drm_connector_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@xxxxxxxxxx> > > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> > > --- > > drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c > > index 4d4a715b429d..2c2b92324a2e 100644 > > --- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c > > +++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c > > @@ -60,8 +60,9 @@ static int fsl_dcu_drm_connector_get_modes(struct drm_connector *connector) > > return drm_panel_get_modes(fsl_connector->panel, connector); > > } > > > > -static int fsl_dcu_drm_connector_mode_valid(struct drm_connector *connector, > > - struct drm_display_mode *mode) > > +static enum drm_mode_status > > +fsl_dcu_drm_connector_mode_valid(struct drm_connector *connector, > > + struct drm_display_mode *mode) > > { > > if (mode->hdisplay & 0xf) > > return MODE_ERROR; > > > > base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780 > > -- > > 2.38.1 > > > > > > Could someone please pick this up so that it makes 6.2? We would like > to try and get this warning turned on so that it can catch more > potential run time issues at compile time but that can only happen when > all the warnings are fixed. I'll pick this up tomorrow if no one else snags it. :) -- Kees Cook
