CVE-2024-49964: 
Linux Kernel vulnerability analysis and mitigation

A vulnerability in the Linux kernel's memory management subsystem (CVE-2024-49964) was discovered affecting versions from 6.11 up to (excluding) 6.11.3. The issue involves a memory leak in the hugetlb subsystem where memfd_pin_folios followed by unpin_folios fails to properly restore free_huge_pages when pages were not already faulted in (Kernel Patch).

The vulnerability stems from incorrect reference counting in the memfd_pin_folios function. The issue occurs because the folio refcount for pages created by memfd_alloc_folio never reaches 0 due to multiple reference count additions: one from folio_ref_unfreeze(folio, 1), another from folio_try_get(), and 512 from hugetlb_add_to_page_cache() on x86 systems. The CVSS v3.1 base score is 5.5 (Medium) with vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (NVD).

The vulnerability results in a memory leak in the Linux kernel's huge pages management system. When memfd_pin_folios is followed by unpin_folios operations, it fails to properly restore free_huge_pages if the pages were not already faulted in, potentially leading to resource exhaustion (Kernel Patch).

The vulnerability requires local access with low privileges to exploit. No public exploits have been identified in the wild. The attack complexity is considered low, requiring no user interaction to exploit (NVD).

The issue has been fixed in Linux kernel version 6.11.3. The patch adds an additional folio_put call when h (hstate) is present to properly handle the reference counting. System administrators should upgrade affected systems to the patched version (Kernel Patch).