In Android before 2018-04-05 or earlier security patch level on Qualcomm Snapdragon Mobile, Snapdragon Wear, and Small Cell SoC FSM9055, IPQ4019, MDM9206, MDM9607, MDM9625, MDM9635M, MDM9640, MDM9645, MDM9650, MDM9655, MSM8909W, SD 210/SD 212/SD 205, SD 400, SD 410/12, SD 600, SD 615/16/SD 415, SD 617, SD 650/52, SD 800, SD 808, SD 810, SD 835, and SDX20, the reserved memory of TZ subsystem (like TZ apps and some PIL image subsystem) is not cleared after being used.