[PATCH 2/3] thermal/drivers/qcom/tsens: Validate the sensor count before initialization

[Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>]

The #qcom,sensors property can override the platform sensor count without
an upper-bound check. A count exceeding the IP's maximum causes the
driver to access uninitialized regmap fields when handling interrupts.
Platforms with an explicit hardware-ID table can also read beyond that
table, even when the count remains within the IP's hardware limit.

Reject zero counts and counts exceeding the hardware maximum or, when
present, the hardware-ID table length before allocating the private
structure and assigning sensor IDs. Preserve the existing fallback to
the platform default when the property cannot be read, and document
both the fallback and the sensor-count limits.

Fixes: 6d7c70d1cd65 ("thermal: qcom: tsens: Allow number of sensors to come from DT")
Closes: https://sashiko.dev/#/bug/linux-d0867095-c131-491e-a6aa-a81debfd0df5
Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
Cc: Bjorn Andersson <andersson@kernel.org>
---
 drivers/thermal/qcom/tsens.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/qcom/tsens.c b/drivers/thermal/qcom/tsens.c
index 4f69ce4976d9..9134637a3458 100644
--- a/drivers/thermal/qcom/tsens.c
+++ b/drivers/thermal/qcom/tsens.c
@@ -1399,10 +1399,20 @@ static int tsens_probe_common(struct platform_device *pdev)
 
 	num_sensors = data->num_sensors;
 
+	/*
+	 * DT may override the platform sensor count. A missing, empty or too
+	 * short property leaves num_sensors unchanged, retaining the default.
+	 */
 	if (np)
 		of_property_read_u32(np, "#qcom,sensors", &num_sensors);
 
-	if (num_sensors <= 0) {
+	/*
+	 * Require at least one sensor and stay within the IP's hardware limit.
+	 * Platforms with an explicit hardware-ID table also limit the count to
+	 * its number of entries, which may be smaller than the hardware limit.
+	 */
+	if (!num_sensors || num_sensors > data->feat->max_sensors ||
+	    (data->hw_ids && num_sensors > data->num_sensors)) {
 		dev_err(dev, "%s: invalid number of sensors\n", __func__);
 		return -EINVAL;
 	}
-- 
2.43.0