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

Subsystems: drm drivers, drm drivers and misc gpu patches, the rest

STALE1957d

6 messages, 4 authors, 2021-03-24 · open the first message on its own page

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

From: Arnd Bergmann <arnd@kernel.org>
Date: 2021-03-23 13:06:56

From: Arnd Bergmann <arnd@arndb.de>

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 <arnd@arndb.de>
---
 drivers/gpu/drm/imx/imx-ldb.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
index dbfe39e2f7f6..1210360cec8a 100644
--- a/drivers/gpu/drm/imx/imx-ldb.c
+++ b/drivers/gpu/drm/imx/imx-ldb.c
@@ -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__);
-- 
2.29.2


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Re: [PATCH] drm/imx: fix out of bounds array access warning

From: Fabio Estevam <festevam@gmail.com>
Date: 2021-03-23 14:03:07

Hi Arnd,

On Tue, Mar 23, 2021 at 10:05 AM Arnd Bergmann [off-list ref] wrote:
From: Arnd Bergmann <arnd@arndb.de>

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) ?
--- a/drivers/gpu/drm/imx/Kconfig
+++ b/drivers/gpu/drm/imx/Kconfig
@@ -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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Re: [PATCH] drm/imx: fix out of bounds array access warning

From: Liu Ying <victor.liu@nxp.com>
Date: 2021-03-24 03:06:10

Hi Fabio,

On Tue, 2021-03-23 at 11:02 -0300, Fabio Estevam wrote:
Hi Arnd,

On Tue, Mar 23, 2021 at 10:05 AM Arnd Bergmann [off-list ref] wrote:
quoted
From: Arnd Bergmann <arnd@arndb.de>

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
quoted hunk
--- a/drivers/gpu/drm/imx/Kconfig
+++ b/drivers/gpu/drm/imx/Kconfig
@@ -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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Re: [PATCH] drm/imx: fix out of bounds array access warning

From: Joe Perches <joe@perches.com>
Date: 2021-03-23 14:19:58

On Tue, 2021-03-23 at 14:05 +0100, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@arndb.de>

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.
[]
quoted hunk
diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
[]
quoted hunk
@@ -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));
quoted hunk
@@ -255,6 +261,12 @@ imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,
[]
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);
etc...



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Re: [PATCH] drm/imx: fix out of bounds array access warning

From: Liu Ying <victor.liu@nxp.com>
Date: 2021-03-24 02:53:50

On Tue, 2021-03-23 at 07:19 -0700, Joe Perches wrote:
On Tue, 2021-03-23 at 14:05 +0100, Arnd Bergmann wrote:
quoted
From: Arnd Bergmann <arnd@arndb.de>

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.
[]
quoted
diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
[]
quoted
@@ -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));
+1

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

Regards,
Liu Ying
quoted
@@ -255,6 +261,12 @@ imx_ldb_encoder_atomic_mode_set(struct drm_encoder *encoder,
[]
quoted
+	if (mux < 0) {
+		dev_warn(ldb->dev,
+			 "%s: invalid mux\n", __func__);
etc...

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Re: [PATCH] drm/imx: fix out of bounds array access warning

From: Liu Ying <victor.liu@nxp.com>
Date: 2021-03-24 03:32:55

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

On Tue, 2021-03-23 at 14:05 +0100, Arnd Bergmann wrote:
quoted hunk
From: Arnd Bergmann <arnd@arndb.de>

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 <arnd@arndb.de>
---
 drivers/gpu/drm/imx/imx-ldb.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
index dbfe39e2f7f6..1210360cec8a 100644
--- a/drivers/gpu/drm/imx/imx-ldb.c
+++ b/drivers/gpu/drm/imx/imx-ldb.c
@@ -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__);

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