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drm/sti: Fix return type of sti_{dvo,hda,hdmi}_connector_mode_valid()

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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>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221102155623.3042869-1-nathan@kernel.org
This commit is contained in:
Nathan Chancellor 2022-11-02 08:56:23 -07:00 committed by Kees Cook
parent 96d845a67b
commit 0ad811cc08
3 changed files with 9 additions and 6 deletions
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3
drivers/gpu/drm/sti/sti_dvo.c
View File

@ -346,7 +346,8 @@ static int sti_dvo_connector_get_modes(struct drm_connector *connector)
#define CLK_TOLERANCE_HZ 50
static int sti_dvo_connector_mode_valid(struct drm_connector *connector,
static enum drm_mode_status
sti_dvo_connector_mode_valid(struct drm_connector *connector,
struct drm_display_mode *mode)
{
int target = mode->clock * 1000;

3
drivers/gpu/drm/sti/sti_hda.c
View File

@ -601,7 +601,8 @@ static int sti_hda_connector_get_modes(struct drm_connector *connector)
#define CLK_TOLERANCE_HZ 50
static int sti_hda_connector_mode_valid(struct drm_connector *connector,
static enum drm_mode_status
sti_hda_connector_mode_valid(struct drm_connector *connector,
struct drm_display_mode *mode)
{
int target = mode->clock * 1000;

3
drivers/gpu/drm/sti/sti_hdmi.c
View File

@ -1004,7 +1004,8 @@ fail:
#define CLK_TOLERANCE_HZ 50
static int sti_hdmi_connector_mode_valid(struct drm_connector *connector,
static enum drm_mode_status
sti_hdmi_connector_mode_valid(struct drm_connector *connector,
struct drm_display_mode *mode)
{
int target = mode->clock * 1000;