2021-10-04 19:29:40

by Marijn Suijten

Subject: [PATCH 04/10] backlight: qcom-wled: Validate enabled string indices in DT

The strings passed in DT may possibly cause out-of-bounds register
accesses and should be validated before use.

Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
Signed-off-by: Marijn Suijten <[email protected]>
Reviewed-by: AngeloGioacchino Del Regno <[email protected]>
---
drivers/video/backlight/qcom-wled.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
index 29910e603c42..27e8949c7922 100644
--- a/drivers/video/backlight/qcom-wled.c
+++ b/drivers/video/backlight/qcom-wled.c
@@ -1526,6 +1526,12 @@ static int wled_configure(struct wled *wled)
"qcom,enabled-strings",
sizeof(u32));
if (string_len > 0) {
+ if (string_len > wled->max_string_count) {
+ dev_err(dev, "Cannot have more than %d strings\n",
+ wled->max_string_count);
+ return -EINVAL;
+ }
+
rc = of_property_read_u32_array(dev->of_node,
"qcom,enabled-strings",
wled->cfg.enabled_strings,
@@ -1537,6 +1543,14 @@ static int wled_configure(struct wled *wled)
return -EINVAL;
}

+ for (i = 0; i < string_len; ++i) {
+ if (wled->cfg.enabled_strings[i] >= wled->max_string_count) {
+ dev_err(dev, "qcom,enabled-strings index %d at %d is out of bounds\n",
+ wled->cfg.enabled_strings[i], i);
+ return -EINVAL;
+ }
+ }
+
cfg->num_strings = string_len;
}

--
2.33.0

2021-10-05 09:17:37

by Daniel Thompson

Subject: Re: [PATCH 04/10] backlight: qcom-wled: Validate enabled string indices in DT

On Mon, Oct 04, 2021 at 09:27:35PM +0200, Marijn Suijten wrote:
> The strings passed in DT may possibly cause out-of-bounds register
> accesses and should be validated before use.
>
> Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")

The first half of this patch actually fixes patch 1 from this patch set.
It would be better to move that code there.


Daniel.


> Signed-off-by: Marijn Suijten <[email protected]>
> Reviewed-by: AngeloGioacchino Del Regno <[email protected]>
> ---
> drivers/video/backlight/qcom-wled.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index 29910e603c42..27e8949c7922 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c
> @@ -1526,6 +1526,12 @@ static int wled_configure(struct wled *wled)
> "qcom,enabled-strings",
> sizeof(u32));
> if (string_len > 0) {
> + if (string_len > wled->max_string_count) {
> + dev_err(dev, "Cannot have more than %d strings\n",
> + wled->max_string_count);
> + return -EINVAL;
> + }
> +
> rc = of_property_read_u32_array(dev->of_node,
> "qcom,enabled-strings",
> wled->cfg.enabled_strings,
> @@ -1537,6 +1543,14 @@ static int wled_configure(struct wled *wled)
> return -EINVAL;
> }
>
> + for (i = 0; i < string_len; ++i) {
> + if (wled->cfg.enabled_strings[i] >= wled->max_string_count) {
> + dev_err(dev, "qcom,enabled-strings index %d at %d is out of bounds\n",
> + wled->cfg.enabled_strings[i], i);
> + return -EINVAL;
> + }
> + }
> +
> cfg->num_strings = string_len;
> }
>
> --
> 2.33.0
>

2021-10-05 10:06:39

by Marijn Suijten

Subject: Re: [PATCH 04/10] backlight: qcom-wled: Validate enabled string indices in DT

On 2021-10-05 10:14:52, Daniel Thompson wrote:
> On Mon, Oct 04, 2021 at 09:27:35PM +0200, Marijn Suijten wrote:
> > The strings passed in DT may possibly cause out-of-bounds register
> > accesses and should be validated before use.
> >
> > Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
>
> The first half of this patch actually fixes patch 1 from this patch set.
> It would be better to move that code there.

It only helps guarding against a maximum of 3 leds for WLED3, while
using string_len instead of an unintentional sizeof(u32) (resulting in
a fixed size of 4) is a different issue requiring a separate patch to
fix.

Would it help to reorder this patch before 1/10, and mention in patch
1/10 (then 2/10) that, besides properly using string_len instead of
hardcoded 4 (which causes wrong reads from DT on top of this), it relies
on the previous patch to prevent against an array longer than 3 for
WLED3?

- Marijn

> Daniel.
>
>
> > Signed-off-by: Marijn Suijten <[email protected]>
> > Reviewed-by: AngeloGioacchino Del Regno <[email protected]>
> > ---
> > drivers/video/backlight/qcom-wled.c | 14 ++++++++++++++
> > 1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> > index 29910e603c42..27e8949c7922 100644
> > --- a/drivers/video/backlight/qcom-wled.c
> > +++ b/drivers/video/backlight/qcom-wled.c
> > @@ -1526,6 +1526,12 @@ static int wled_configure(struct wled *wled)
> > "qcom,enabled-strings",
> > sizeof(u32));
> > if (string_len > 0) {
> > + if (string_len > wled->max_string_count) {
> > + dev_err(dev, "Cannot have more than %d strings\n",
> > + wled->max_string_count);
> > + return -EINVAL;
> > + }
> > +
> > rc = of_property_read_u32_array(dev->of_node,
> > "qcom,enabled-strings",
> > wled->cfg.enabled_strings,
> > @@ -1537,6 +1543,14 @@ static int wled_configure(struct wled *wled)
> > return -EINVAL;
> > }
> >
> > + for (i = 0; i < string_len; ++i) {
> > + if (wled->cfg.enabled_strings[i] >= wled->max_string_count) {
> > + dev_err(dev, "qcom,enabled-strings index %d at %d is out of bounds\n",
> > + wled->cfg.enabled_strings[i], i);
> > + return -EINVAL;
> > + }
> > + }
> > +
> > cfg->num_strings = string_len;
> > }
> >
> > --
> > 2.33.0
> >

2021-10-05 10:43:48

by Daniel Thompson

Subject: Re: [PATCH 04/10] backlight: qcom-wled: Validate enabled string indices in DT

On Tue, Oct 05, 2021 at 12:03:50PM +0200, Marijn Suijten wrote:
> On 2021-10-05 10:14:52, Daniel Thompson wrote:
> > On Mon, Oct 04, 2021 at 09:27:35PM +0200, Marijn Suijten wrote:
> > > The strings passed in DT may possibly cause out-of-bounds register
> > > accesses and should be validated before use.
> > >
> > > Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
> >
> > The first half of this patch actually fixes patch 1 from this patch set.
> > It would be better to move that code there.
>
> It only helps guarding against a maximum of 3 leds for WLED3, while
> using string_len instead of an unintentional sizeof(u32) (resulting in
> a fixed size of 4) is a different issue requiring a separate patch to
> fix.
>
> Would it help to reorder this patch before 1/10, and mention in patch
> 1/10 (then 2/10) that, besides properly using string_len instead of
> hardcoded 4 (which causes wrong reads from DT on top of this), it relies
> on the previous patch to prevent against an array longer than 3 for
> WLED3?

Reordering is OK for me.


Daniel.


> > > Signed-off-by: Marijn Suijten <[email protected]>
> > > Reviewed-by: AngeloGioacchino Del Regno <[email protected]>
> > > ---
> > > drivers/video/backlight/qcom-wled.c | 14 ++++++++++++++
> > > 1 file changed, 14 insertions(+)
> > >
> > > diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> > > index 29910e603c42..27e8949c7922 100644
> > > --- a/drivers/video/backlight/qcom-wled.c
> > > +++ b/drivers/video/backlight/qcom-wled.c
> > > @@ -1526,6 +1526,12 @@ static int wled_configure(struct wled *wled)
> > > "qcom,enabled-strings",
> > > sizeof(u32));
> > > if (string_len > 0) {
> > > + if (string_len > wled->max_string_count) {
> > > + dev_err(dev, "Cannot have more than %d strings\n",
> > > + wled->max_string_count);
> > > + return -EINVAL;
> > > + }
> > > +
> > > rc = of_property_read_u32_array(dev->of_node,
> > > "qcom,enabled-strings",
> > > wled->cfg.enabled_strings,
> > > @@ -1537,6 +1543,14 @@ static int wled_configure(struct wled *wled)
> > > return -EINVAL;
> > > }
> > >
> > > + for (i = 0; i < string_len; ++i) {
> > > + if (wled->cfg.enabled_strings[i] >= wled->max_string_count) {
> > > + dev_err(dev, "qcom,enabled-strings index %d at %d is out of bounds\n",
> > > + wled->cfg.enabled_strings[i], i);
> > > + return -EINVAL;
> > > + }
> > > + }
> > > +
> > > cfg->num_strings = string_len;
> > > }
> > >
> > > --
> > > 2.33.0
> > >