ARM Platform Uses Signed Integer Comparison When Validating Syscall Numbers

The arm platform-specific code uses a signed integer comparison when validating system call numbers. An attacker who has obtained code execution within a user thread is able to elevate privileges to that of the kernel. See NCC-ZEP-001 This issue affects: zephyrproject-rtos zephyr version 1.14.0 and later versions. version 2.1.0 and later versions.