drm/imx: fix out of bounds array access warning

Message ID 20210323130550.2289487-1-arnd@kernel.org
State Superseded
Headers show
Series
  • drm/imx: fix out of bounds array access warning
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Commit Message

Arnd Bergmann March 23, 2021, 1:05 p.m.
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(+)

-- 
2.29.2

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Comments

Fabio Estevam March 23, 2021, 2:02 p.m. | #1
Hi Arnd,

On Tue, Mar 23, 2021 at 10:05 AM Arnd Bergmann <arnd@kernel.org> 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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Joe Perches March 23, 2021, 2:19 p.m. | #2
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.

[]
> diff --git 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__);


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));

> @@ -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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Liu Ying March 24, 2021, 2:50 a.m. | #3
On Tue, 2021-03-23 at 07:19 -0700, Joe Perches wrote:
> 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.

> []

> > diff --git 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__);

> 

> 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

> 

> > @@ -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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Liu Ying March 24, 2021, 3:03 a.m. | #4
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 <arnd@kernel.org> 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) ?


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

> 

> --- 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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Liu Ying March 24, 2021, 3:30 a.m. | #5
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:
> 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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Patch

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__);