On 2021-10-05 10:14:52, Daniel Thompson wrote:

On Mon, Oct 04, 2021 at 09:27:35PM +0200, Marijn Suijten wrote:

quoted

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.

quoted

Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: AngeloGioacchino Del Regno <redacted>
---
 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