[PATCH AUTOSEL 4.19 1/3] drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid()

[PATCH AUTOSEL 4.19 1/3] drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid()

[Sasha Levin]

From: Nathan Chancellor <nathan@kernel.org>

[ Upstream commit 96d845a67b7e406cfed7880a724c8ca6121e022e ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 2298ed2a9e1c..3c8c4a820e95 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c
@@ -83,8 +83,9 @@ static int fsl_dcu_drm_connector_get_modes(struct drm_connector *connector)
 	return num_modes;
 }
 
-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;
-- 
2.35.1

[PATCH AUTOSEL 4.19 2/3] drm/sti: Fix return type of sti_{dvo,hda,hdmi}_connector_mode_valid()

[Sasha Levin]

From: Nathan Chancellor <nathan@kernel.org>

[ Upstream commit 0ad811cc08a937d875cbad0149c1bab17f84ba05 ]

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>
---
 drivers/gpu/drm/sti/sti_dvo.c  | 5 +++--
 drivers/gpu/drm/sti/sti_hda.c  | 5 +++--
 drivers/gpu/drm/sti/sti_hdmi.c | 5 +++--
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/sti/sti_dvo.c b/drivers/gpu/drm/sti/sti_dvo.c
index b08376b7611b..08d096822f24 100644
--- a/drivers/gpu/drm/sti/sti_dvo.c
+++ b/drivers/gpu/drm/sti/sti_dvo.c
@@ -346,8 +346,9 @@ 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 19b9b5ed1297..9974c19c04c4 100644
--- a/drivers/gpu/drm/sti/sti_hda.c
+++ b/drivers/gpu/drm/sti/sti_hda.c
@@ -596,8 +596,9 @@ 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 ccf718404a1c..b5199dd4b817 100644
--- a/drivers/gpu/drm/sti/sti_hdmi.c
+++ b/drivers/gpu/drm/sti/sti_hdmi.c
@@ -989,8 +989,9 @@ static int sti_hdmi_connector_get_modes(struct drm_connector *connector)
 
 #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;
-- 
2.35.1