powerpc/pseries/memhp: Fix access beyond end of drmem array

CVE-2023-52451

What is CVE-2023-52451?

A vulnerability in the Linux kernel's handling of memory hotplugging specifically affects the PowerPC Pseries systems. The issue arises when the function 'dlpar_memory_remove_by_index()' attempts to access memory beyond the bounds of the data region memory (drmem) local memory block (lmb) array. This can lead to dereferencing a pointer that points to an invalid memory location when looking up a device resource configuration (DRC) index fails. The resulting memory access violation can manifest as a slab-out-of-bounds error, potentially leading to unpredicted disruptions or crashes. The vulnerability has been detected through rigorous inspection and confirmed using the Kernel Address Sanitizer (KASAN). Proper logging and validation of memory access are essential to circumvent this flaw.

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