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drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid() 

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@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221102154215.78059-1-nathan@kernel.org
This commit is contained in:
Nathan Chancellor 2022-11-02 08:42:15 -07:00 committed by Kees Cook
parent 74c8e6bffb
commit 96d845a67b
1 changed files with 3 additions and 2 deletions
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5
drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c
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@ -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;