[PATCH v3] hwmon: (aquacomputer_d5next) valid the data size before reading the sensor data

[Edward Adam Davis]

The user-forged sensor data is only 65 bytes long; however, aqc_raw_event()
fails to handle cases where the sensor data length is too small when reading
the data, resulting in [1] during the read process.

Add a data size check, if the size is less than that required for the
specific data item to be read, abort the sensor data read operation.

[1]
BUG: KASAN: slab-out-of-bounds in aqc_raw_event+0x213e/0x25d0 drivers/hwmon/aquacomputer_d5next.c:1327
Read of size 2 at addr ffff888108aba257 by task swapper/1/0
Call Trace:
 get_unaligned_be16 include/linux/unaligned.h:48 [inline]
 aqc_raw_event drivers/hwmon/aquacomputer_d5next.c:1345 [inline]
 aqc_raw_event+0x213e/0x25d0 drivers/hwmon/aquacomputer_d5next.c:1327
 __hid_input_report.constprop.0+0x319/0x470 drivers/hid/hid-core.c:2168
 hid_irq_in+0x55d/0x710 drivers/hid/usbhid/hid-core.c:287
 __usb_hcd_giveback_urb+0x38d/0x610 drivers/usb/core/hcd.c:1657
 usb_hcd_giveback_urb+0x3ca/0x4a0 drivers/usb/core/hcd.c:1741

Fixes: 0e35f63f7f4e ("hwmon: add driver for Aquacomputer D5 Next")
Reported-by: syzbot+9ee5f5dc18673d6b2f37@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=9ee5f5dc18673d6b2f37
Tested-by: syzbot+9ee5f5dc18673d6b2f37@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
v1 -> v2: change to check the data item and update comments
v2 -> v3: check all sub items and update subject

 drivers/hwmon/aquacomputer_d5next.c | 74 +++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/drivers/hwmon/aquacomputer_d5next.c b/drivers/hwmon/aquacomputer_d5next.c
index 1ca70e726298..2381a74eb4a4 100644
--- a/drivers/hwmon/aquacomputer_d5next.c
+++ b/drivers/hwmon/aquacomputer_d5next.c
@@ -1324,6 +1324,77 @@ static const struct hwmon_chip_info aqc_chip_info = {
 	.info = aqc_info,
 };
 
+static bool aqc_raw_data_valid(struct aqc_data *priv, int size)
+{
+	int off, fan_off, i;
+	char *msg;
+
+	if (!priv)
+		return false;
+
+	/* +1 for get_unaligned_be16(), it reads 2 bytes */
+	off = priv->serial_number_start_offset + SERIAL_PART_OFFSET + 1;
+	if (off >= size) {
+		msg = "serial number start offset";
+		goto invalid;
+	}
+
+	off = priv->firmware_version_offset + 1;
+	if (off >= size) {
+		msg = "firmware version offset";
+		goto invalid;
+	}
+
+	/* Physical temperature sensor readings data size check*/
+	for (i = 0; i < priv->num_temp_sensors; i++) {
+		off = priv->temp_sensor_start_offset + i * AQC_SENSOR_SIZE + 1;
+
+		if (off >= size) {
+			msg = "temp sensor start offset";
+			goto invalid;
+		}
+	}
+
+	/* Virtual temperature sensor readings data size check*/
+	for (i = 0; i < priv->num_virtual_temp_sensors; i++) {
+		off = priv->virtual_temp_sensor_start_offset +
+		      i * AQC_SENSOR_SIZE + 1;
+
+		if (off >= size) {
+			msg = "virtual temp sensor start offset";
+			goto invalid;
+		}
+	}
+
+	/* Fan speed and related readings data size check */
+	for (i = 0; i < priv->num_fans; i++) {
+		fan_off = priv->fan_sensor_offsets[i] + 1;
+		off = fan_off + priv->fan_structure->power;
+		if (off >= size) {
+			msg = "fan power offset";
+			goto invalid;
+		}
+
+		off = fan_off + priv->fan_structure->voltage;
+		if (off >= size) {
+			msg = "fan voltage offset";
+			goto invalid;
+		}
+
+		off = fan_off + priv->fan_structure->curr;
+		if (off >= size) {
+			msg = "fan curr offset";
+			goto invalid;
+		}
+	}
+
+	return true;
+invalid:
+	pr_debug("data size (%d) is less than the %s, %s\n",
+		 size, msg, __func__);
+	return false;
+}
+
 static int aqc_raw_event(struct hid_device *hdev, struct hid_report *report, u8 *data, int size)
 {
 	int i, j, sensor_value;
@@ -1334,6 +1405,9 @@ static int aqc_raw_event(struct hid_device *hdev, struct hid_report *report, u8
 
 	priv = hid_get_drvdata(hdev);
 
+	if (!aqc_raw_data_valid(priv, size))
+		return 0;
+
 	/* Info provided with every report */
 	priv->serial_number[0] = get_unaligned_be16(data + priv->serial_number_start_offset);
 	priv->serial_number[1] = get_unaligned_be16(data + priv->serial_number_start_offset +
-- 
2.43.0