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 parsing the
property separately much like qcom,enabled-strings.
This also allows more stringent checks on the maximum value when
qcom,enabled-strings is provided in the DT. Note that num-strings is
parsed after enabled-strings to give it final sign-off over the length,
which DT currently utilizes to get around an incorrect fixed read of
four elements from that array (has been addressed in a prior patch).
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 | 51 +++++++++++------------------
1 file changed, 19 insertions(+), 32 deletions(-)
diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
index 977cd75827d7..c5232478a343 100644
--- a/drivers/video/backlight/qcom-wled.c
+++ b/drivers/video/backlight/qcom-wled.c
@@ -1253,21 +1253,6 @@ static const struct wled_var_cfg wled5_ovp_cfg = {
.size = 16,
};
-static u32 wled3_num_strings_values_fn(u32 idx)
-{
- return idx + 1;
-}
-
-static const struct wled_var_cfg wled3_num_strings_cfg = {
- .fn = wled3_num_strings_values_fn,
- .size = 3,
-};
-
-static const struct wled_var_cfg wled4_num_strings_cfg = {
- .fn = wled3_num_strings_values_fn,
- .size = 4,
-};
-
static u32 wled3_switch_freq_values_fn(u32 idx)
{
return 19200 / (2 * (1 + idx));
@@ -1341,11 +1326,6 @@ static int wled_configure(struct wled *wled)
.val_ptr = &cfg->switch_freq,
.cfg = &wled3_switch_freq_cfg,
},
- {
- .name = "qcom,num-strings",
- .val_ptr = &cfg->num_strings,
- .cfg = &wled3_num_strings_cfg,
- },
};
const struct wled_u32_opts wled4_opts[] = {
@@ -1369,11 +1349,6 @@ static int wled_configure(struct wled *wled)
.val_ptr = &cfg->switch_freq,
.cfg = &wled3_switch_freq_cfg,
},
- {
- .name = "qcom,num-strings",
- .val_ptr = &cfg->num_strings,
- .cfg = &wled4_num_strings_cfg,
- },
};
const struct wled_u32_opts wled5_opts[] = {
@@ -1397,11 +1372,6 @@ static int wled_configure(struct wled *wled)
.val_ptr = &cfg->switch_freq,
.cfg = &wled3_switch_freq_cfg,
},
- {
- .name = "qcom,num-strings",
- .val_ptr = &cfg->num_strings,
- .cfg = &wled4_num_strings_cfg,
- },
{
.name = "qcom,modulator-sel",
.val_ptr = &cfg->mod_sel,
@@ -1520,8 +1490,6 @@ 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));
@@ -1552,6 +1520,25 @@ static int wled_configure(struct wled *wled)
}
}
+ rc = of_property_read_u32(dev->of_node, "qcom,num-strings", &val);
+ if (!rc) {
+ if (val < 1 || val > wled->max_string_count) {
+ dev_err(dev, "qcom,num-strings must be between 1 and %d\n",
+ wled->max_string_count);
+ return -EINVAL;
+ }
+
+ if (string_len > 0) {
+ dev_warn(dev, "qcom,num-strings and qcom,enabled-strings are ambiguous\n");
+ if (val > string_len) {
+ dev_err(dev, "qcom,num-strings exceeds qcom,enabled-strings\n");
+ return -EINVAL;
+ }
+ }
+
+ cfg->num_strings = val;
+ }
+
return 0;
}
--
2.33.0
