Local code execution via unchecked command length

Buffer overflow in Linux papr-phy-attest code allows local users to crash the kernel or execute code through an oversized command. papr_phy_attest_create_handle() uses params->cmd.length without checking for zero or a value larger than params->cmd, allowing the command to overrun the buffer; error and negative-fd paths also leak params. Exploitation requires local low-privileged access in a PowerPC pSeries environment where papr-phy-attest is reachable, and the bounded consequences are kernel memory corruption, code execution, or a crash.