2021-03-23 13:11:10

by Arnd Bergmann

Subject: [PATCH] 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(+)

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

2021-03-23 14:07:27

by Fabio Estevam

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

Hi Arnd,

On Tue, Mar 23, 2021 at 10:05 AM Arnd Bergmann <[email protected]> wrote:
>
> 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) ?

--- 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

2021-03-23 14:23:39

by Joe Perches

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

On Tue, 2021-03-23 at 14:05 +0100, Arnd Bergmann wrote:
> 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.
[]
> 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...

2021-03-24 09:41:39

by Liu Ying

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

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 <[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(+)
>
> 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__);

2021-03-24 22:00:37

by Liu Ying

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

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 <[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.
> []
> > 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...
>
>

2021-03-24 22:06:07

by Liu Ying

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

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 <[email protected]> wrote:
> > 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) ?

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