CVE-2024-40974 addresses a vulnerability in the Linux kernel's powerpc/pseries subsystem related to hypervisor call (hcall) result buffer handling. The issue arises because functions like plpar_hcall() and plpar_hcall9() expect callers to provide result buffers of a minimum size, but this requirement was only documented in comments, not enforced by the compiler. This could lead to stack corruption if a buffer smaller than required is passed. The fix enforces buffer size validity by using explicitly-sized array parameters, enabling compiler diagnostics to catch undersized buffers during compilation.