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 <marijn.suijten@somainline.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211115203459.1634079-2-marijn.suijten@somainline.org

diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
index d094299c2a485bf685e856f0335d84f15e88bc43..8a42ed89c59c9698998bb818c3a76eb4b17d3f44 100644 (file)
--- a/drivers/video/backlight/qcom-wled.c
+++ b/drivers/video/backlight/qcom-wled.c
@@ -1528,12 +1528,28 @@ static int wled_configure(struct wled *wled)
        string_len = of_property_count_elems_of_size(dev->of_node,
                                                     "qcom,enabled-strings",
                                                     sizeof(u32));
-       if (string_len > 0)
+       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;
+               }
+
                of_property_read_u32_array(dev->of_node,
                                                "qcom,enabled-strings",
                                                wled->cfg.enabled_strings,
                                                sizeof(u32));
 
+               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;
+                       }
+               }
+       }
+
        return 0;
 }