[PATCH] proc: Don't allow empty /proc/PID/cmdline for user tasks Kernel threads have empty /proc/PID/cmdline and some userland tools including ps(1) and older versions of systemd use this to detect kernel threads. However, any userland program can emulate the behavior by making its argvs unavailable and trick the affected tools into thinking that the task is a kernel thread. Linus's reproducer fol