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drm/imx: fix out of bounds array access warning

PATCH Superseded Arnd Bergmann 4 participants 6 messages Mar 23, 2021 – Mar 24, 2021

Subsystems (3)
DRM drivers DRM misc Arm i.MX and Layerscape

v1 of 3 Superseded Latest is v3 →

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Arnd Bergmann

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#0 lore raw

PATCH 1/1 drm/imx: fix out of bounds array access warning

From: Arnd Bergmann <[email protected]>

When CONFIG_OF is disabled, building with 'make W=1' produces warnings about out of bounds array access:

drivers/gpu/drm/imx/imx-ldb.c: In function 'imx_ldb_set_clock.constprop':
drivers/gpu/drm/imx/imx-ldb.c:186:8: error: array subscript -22 is below array bounds of 'struct clk *[4]' [-Werror=array-bounds]

Add an error check before the index is used, which helps with the warning, as well as any possible other error condition that may be triggered at runtime.

Signed-off-by Arnd Bergmann <[email protected]>
---
 drivers/gpu/drm/imx/imx-ldb.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
drivers/gpu/drm/imx/imx-ldb.c +12 -0
index dbfe39e2f7f6..1210360cec8a 100644
@@ -197,6 +197,12 @@ static void imx_ldb_encoder_enable(struct drm_encoder *encoder)
 	int dual = ldb->ldb_ctrl & LDB_SPLIT_MODE_EN;
 	int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
 
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);
+		return;
+	}
+
 	drm_panel_prepare(imx_ldb_ch->panel);
 
 	if (dual) {

@@ -255,6 +261,12 @@ imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,
 	int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
 	u32 bus_format = imx_ldb_ch->bus_format;
 
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);
+		return;
+	}
+
 	if (mode->clock > 170000) {
 		dev_warn(ldb->dev,
 			 "%s: mode exceeds 170 MHz pixel clock\n", __func__);
Signature · 6 lines
2.29.2

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#1 lore raw

Hi Arnd,

Quoted 8 lines · Arnd Bergmann

From: Arnd Bergmann <[email protected]>

When CONFIG_OF is disabled, building with 'make W=1' produces warnings about out of bounds array access:

drivers/gpu/drm/imx/imx-ldb.c: In function 'imx_ldb_set_clock.constprop':
drivers/gpu/drm/imx/imx-ldb.c:186:8: error: array subscript -22 is below array bounds of 'struct clk *[4]' [-Werror=array-bounds]

What about making the driver depend on OF instead (like it is done in DRM_IMX_HDMI) ?

drivers/gpu/drm/imx/Kconfig +1 -1
@@ -27,7 +27,7 @@ config DRM_IMX_TVE
 
 config DRM_IMX_LDB
        tristate "Support for LVDS displays"
-       depends on DRM_IMX && MFD_SYSCON
+       depends on DRM_IMX && MFD_SYSCON && OF
        depends on COMMON_CLK
        select DRM_PANEL
        help

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#2 lore raw

Hi Fabio,

Quoted 5 lines · Fabio Estevam

Hi Arnd,

Quoted 2 lines · Arnd Bergmann

From: Arnd Bergmann <[email protected]>

Quoted 8 lines
Quoted 5 lines

When CONFIG_OF is disabled, building with 'make W=1' produces warnings about out of bounds array access:

drivers/gpu/drm/imx/imx-ldb.c: In function 'imx_ldb_set_clock.constprop':
drivers/gpu/drm/imx/imx-ldb.c:186:8: error: array subscript -22 is below array bounds of 'struct clk *[4]' [-Werror=array-bounds]

What about making the driver depend on OF instead (like it is done in DRM_IMX_HDMI) ?

The below patch made DRM_IMX_HDMI depend on OF, because of_drm_find_bridge() is not defined when OF is disabled.

drm/imx: dw_hdmi-imx: depend on OF to fix randconfig compile tests on x86_64

It doesn't look like DRM_IMX_LDB is in the same case.

Moreover, even if OF is enabled, drm_of_encoder_active_endpoint() is likely to return -EINVAL. So, it looks ok to add an error check.

Regards,
Liu Ying

drivers/gpu/drm/imx/Kconfig config DRM_IMX_TVE · line 33

Quoted 12 lines
drivers/gpu/drm/imx/Kconfig +1 -1
@@ -27,7 +27,7 @@ config DRM_IMX_TVE
 
 config DRM_IMX_LDB
        tristate "Support for LVDS displays"
-       depends on DRM_IMX && MFD_SYSCON
+       depends on DRM_IMX && MFD_SYSCON && OF
        depends on COMMON_CLK
        select DRM_PANEL
        help

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#3 lore raw
In reply to Arnd Bergmann
Quoted 11 lines · Arnd Bergmann

From: Arnd Bergmann <[email protected]>

When CONFIG_OF is disabled, building with 'make W=1' produces warnings about out of bounds array access:

drivers/gpu/drm/imx/imx-ldb.c: In function 'imx_ldb_set_clock.constprop':
drivers/gpu/drm/imx/imx-ldb.c:186:8: error: array subscript -22 is below array bounds of 'struct clk *[4]' [-Werror=array-bounds]

Add an error check before the index is used, which helps with the warning, as well as any possible other error condition that may be triggered at runtime.

[]

drivers/gpu/drm/imx/imx-ldb.c

Quoted 1 line
drivers/gpu/drm/imx/imx-ldb.c +0 -0

[]

drivers/gpu/drm/imx/imx-ldb.c static void imx_ldb_encoder_enable(struct drm_encoder *encoder) · line 202

Quoted 7 lines
drivers/gpu/drm/imx/imx-ldb.c +3 -0
@@ -197,6 +197,12 @@ static void imx_ldb_encoder_enable(struct drm_encoder *encoder)
  	int dual = ldb->ldb_ctrl & LDB_SPLIT_MODE_EN;
  	int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
 
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);

trivia:

Any real reason to make this 2 lines? It fits nicely in 80 chars. Maybe:

		dev_warn(ldb->dev, "%s: invalid mux: %d\n", __func__, mux);

or maybe:

		dev_warn(ldb->dev, "%s: invalid mux: %pe\n",
			 __func__, ERR_PTR(mux));

drivers/gpu/drm/imx/imx-ldb.c imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,

Quoted 1 line
drivers/gpu/drm/imx/imx-ldb.c +0 -0
@@ -255,6 +261,12 @@ imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,

[]

drivers/gpu/drm/imx/imx-ldb.c static void imx_ldb_encoder_enable(struct drm_encoder *encoder) · line 202

Quoted 3 lines
drivers/gpu/drm/imx/imx-ldb.c +3 -0
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);

etc...

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#4 lore raw
Quoted 25 lines · Joe Perches
Quoted 11 lines · Arnd Bergmann

From: Arnd Bergmann <[email protected]>

When CONFIG_OF is disabled, building with 'make W=1' produces warnings about out of bounds array access:

drivers/gpu/drm/imx/imx-ldb.c: In function 'imx_ldb_set_clock.constprop':
drivers/gpu/drm/imx/imx-ldb.c:186:8: error: array subscript -22 is below array bounds of 'struct clk *[4]' [-Werror=array-bounds]

Add an error check before the index is used, which helps with the warning, as well as any possible other error condition that may be triggered at runtime.

[]

drivers/gpu/drm/imx/imx-ldb.c

Quoted 1 line
drivers/gpu/drm/imx/imx-ldb.c +0 -0

[]

drivers/gpu/drm/imx/imx-ldb.c static void imx_ldb_encoder_enable(struct drm_encoder *encoder) · line 202

Quoted 7 lines
drivers/gpu/drm/imx/imx-ldb.c +3 -0
@@ -197,6 +197,12 @@ static void imx_ldb_encoder_enable(struct drm_encoder *encoder)
 	int dual = ldb->ldb_ctrl & LDB_SPLIT_MODE_EN;
 	int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
 
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);

trivia:

Quoted 8 lines

Any real reason to make this 2 lines? It fits nicely in 80 chars. Maybe:

		dev_warn(ldb->dev, "%s: invalid mux: %d\n", __func__, mux);

or maybe:

		dev_warn(ldb->dev, "%s: invalid mux: %pe\n",
			 __func__, ERR_PTR(mux));

+1

The second one looks better as it's more informative.

Regards,
Liu Ying

Quoted 10 lines

drivers/gpu/drm/imx/imx-ldb.c imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,

Quoted 2 lines
drivers/gpu/drm/imx/imx-ldb.c +0 -0
@@ -255,6 +261,12 @@ imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,

[]

drivers/gpu/drm/imx/imx-ldb.c static void imx_ldb_encoder_enable(struct drm_encoder *encoder) · line 202

Quoted 3 lines
drivers/gpu/drm/imx/imx-ldb.c +3 -0
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);

etc...

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#5 lore raw
In reply to Arnd Bergmann

Hi Arnd,

Thanks for your patch.

It would be good to improve the patch's head line to something like:
drm/imx: imx-ldb: fix out of bounds array access warning

Regards,
Liu Ying

Quoted 37 lines · Arnd Bergmann

From: Arnd Bergmann <[email protected]>

When CONFIG_OF is disabled, building with 'make W=1' produces warnings about out of bounds array access:

drivers/gpu/drm/imx/imx-ldb.c: In function 'imx_ldb_set_clock.constprop':
drivers/gpu/drm/imx/imx-ldb.c:186:8: error: array subscript -22 is below array bounds of 'struct clk *[4]' [-Werror=array-bounds]

Add an error check before the index is used, which helps with the warning, as well as any possible other error condition that may be triggered at runtime.

Signed-off-by Arnd Bergmann <[email protected]>
---
 drivers/gpu/drm/imx/imx-ldb.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
drivers/gpu/drm/imx/imx-ldb.c +6 -0
index dbfe39e2f7f6..1210360cec8a 100644
@@ -197,6 +197,12 @@ static void imx_ldb_encoder_enable(struct drm_encoder *encoder)
 	int dual = ldb->ldb_ctrl & LDB_SPLIT_MODE_EN;
 	int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
 
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);
+		return;
+	}
+
 	drm_panel_prepare(imx_ldb_ch->panel);
 
 	if (dual) {

@@ -255,6 +261,12 @@ imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,
 	int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
 	u32 bus_format = imx_ldb_ch->bus_format;

drivers/gpu/drm/imx/imx-ldb.c imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder, · line 272

Quoted 10 lines
drivers/gpu/drm/imx/imx-ldb.c +6 -0
 
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);
+		return;
+	}
+
 	if (mode->clock > 170000) {
 		dev_warn(ldb->dev,
 			 "%s: mode exceeds 170 MHz pixel clock\n", __func__);

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