CVE-2024-57881 – Linux Kernel “pfn_to_page” NULL Pointer Dereference Vulnerability in Buddy Allocator

CVE ID : CVE-2024-57881

Published : Jan. 11, 2025, 4:15 p.m. | 23 hours, 50 minutes ago

Description : In the Linux kernel, the following vulnerability has been resolved:

mm/page_alloc: don’t call pfn_to_page() on possibly non-existent PFN in split_large_buddy()

In split_large_buddy(), we might call pfn_to_page() on a PFN that might
not exist. In corner cases, such as when freeing the highest pageblock in
the last memory section, this could result with CONFIG_SPARSEMEM &&
!CONFIG_SPARSEMEM_EXTREME in __pfn_to_section() returning NULL and and
__section_mem_map_addr() dereferencing that NULL pointer.

Let’s fix it, and avoid doing a pfn_to_page() call for the first
iteration, where we already have the page.

So far this was found by code inspection, but let’s just CC stable as the
fix is easy.

Severity: 0.0 | NA

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