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

[ Upstream commit d3b58198abb4e144a3ca3602442d224c612f1bcb ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/sti/sti_dvo.c b/drivers/gpu/drm/sti/sti_dvo.c
index 3c65c73aa8549ad92a18febfd0d026e84061dd3f..d0f1384d0fbaa478960a7780ccc5150897eda715 100644 (file)
--- a/drivers/gpu/drm/sti/sti_dvo.c
+++ b/drivers/gpu/drm/sti/sti_dvo.c
@@ -345,8 +345,9 @@ 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,
-                                       struct drm_display_mode *mode)
+static enum drm_mode_status
+sti_dvo_connector_mode_valid(struct drm_connector *connector,
+                            struct drm_display_mode *mode)
 {
        int target = mode->clock * 1000;
        int target_min = target - CLK_TOLERANCE_HZ;

diff --git a/drivers/gpu/drm/sti/sti_hda.c b/drivers/gpu/drm/sti/sti_hda.c
index 158192680bea0e7370d21b145643c0dba88023b5..b321e55257711e5225fd8957f926344c511b544d 100644 (file)
--- a/drivers/gpu/drm/sti/sti_hda.c
+++ b/drivers/gpu/drm/sti/sti_hda.c
@@ -600,8 +600,9 @@ 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,
-                                       struct drm_display_mode *mode)
+static enum drm_mode_status
+sti_hda_connector_mode_valid(struct drm_connector *connector,
+                            struct drm_display_mode *mode)
 {
        int target = mode->clock * 1000;
        int target_min = target - CLK_TOLERANCE_HZ;

diff --git a/drivers/gpu/drm/sti/sti_hdmi.c b/drivers/gpu/drm/sti/sti_hdmi.c
index c91ce51836ca386afa436c135188c23d91ee7b7a..c5547fedebe30335ffa4f2123887f0b8d60186bb 100644 (file)
--- a/drivers/gpu/drm/sti/sti_hdmi.c
+++ b/drivers/gpu/drm/sti/sti_hdmi.c
@@ -996,8 +996,9 @@ fail:
 
 #define CLK_TOLERANCE_HZ 50
 
-static int sti_hdmi_connector_mode_valid(struct drm_connector *connector,
-                                       struct drm_display_mode *mode)
+static enum drm_mode_status
+sti_hdmi_connector_mode_valid(struct drm_connector *connector,
+                             struct drm_display_mode *mode)
 {
        int target = mode->clock * 1000;
        int target_min = target - CLK_TOLERANCE_HZ;