On Mon, Oct 04, 2021 at 09:27:36PM +0200, Marijn Suijten wrote:
> When not specifying num-strings in the DT the default is used, but +1 is
> added to it which turns wled3 into 4 and wled4/5 into 5 strings instead
> of 3 and 4 respectively, causing out of bounds reads and register
> read/writes. This +1 exists for a deficiency in the DT parsing code,
> and is simply omitted entirely - solving this oob issue - by allowing
> one extra iteration of the wled_var_cfg function parsing this particular
> property.
>
> Fixes: 93c64f1ea1e8 ("leds: add Qualcomm PM8941 WLED driver")
> Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxxx>
> ---
> drivers/video/backlight/qcom-wled.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index 27e8949c7922..66ce77ee3099 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c
> @@ -1255,17 +1255,17 @@ static const struct wled_var_cfg wled5_ovp_cfg = {
>
> static u32 wled3_num_strings_values_fn(u32 idx)
> {
> - return idx + 1;
> + return idx;
> }
>
> static const struct wled_var_cfg wled3_num_strings_cfg = {
> .fn = wled3_num_strings_values_fn,
> - .size = 3,
> + .size = 4, /* [0, 3] */
0 is not a valid value for this property.
> };
>
> static const struct wled_var_cfg wled4_num_strings_cfg = {
> .fn = wled3_num_strings_values_fn,
> - .size = 4,
> + .size = 5, /* [0, 4] */
Ditto.
> };
>
> static u32 wled3_switch_freq_values_fn(u32 idx)
> @@ -1520,8 +1520,6 @@ static int wled_configure(struct wled *wled)
> *bool_opts[i].val_ptr = true;
> }
>
> - cfg->num_strings = cfg->num_strings + 1;
> -
> string_len = of_property_count_elems_of_size(dev->of_node,
> "qcom,enabled-strings",
> sizeof(u32));
> --
> 2.33.0
>
