Linux Kernel MIPS Memory Leak Vulnerability in PGD Management

A memory leak vulnerability has been identified in the Linux kernel's MIPS architecture, specifically related to the management of page directory (PGD) entries. This issue arises when the system allocates more than one page for the PGD table, such as in 64-bit systems with 4KB page sizes and without 48-bit virtual address support. The generic PGD free function, introduced in a previous commit, only frees one page, leading to a memory leak when multiple pages are used. The leak can be detected by monitoring available memory while executing a command that generates file listings.

Impact

Exploitation of this vulnerability leads to a memory leak, causing excessive memory consumption that is not released back to the system.

Reproduction

The vulnerability can be reproduced on a 64-bit Linux system with PAGE_SIZE_4KB enabled and MIPS_VA_BITS_48 disabled. Once this configuration is set, the memory leak can be observed by running a continuous loop that lists directory contents while checking the 'MemFree' statistic in '/proc/meminfo'.