Fix: Add safety check to hwmon read

Avoid panic for accessing slice out of range in hwmon.

Fixes: https://github.com/prometheus/node_exporter/issues/3108

Signed-off-by: Ben Kochie <superq@gmail.com>

collector/hwmon_linux.go

@@ -107,6 +107,9 @@ func sysReadFile(file string) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+	if n < 0 {
+		return nil, fmt.Errorf("failed to read file: %w", file)
+	}
 
 	return b[:n], nil
 }