CVE-2025-37818: LoongArch: Return NULL from huge_pte_offset() for invalid PMD

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-05-08 · updated 2026-06-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: LoongArch: Return NULL from huge_pte_offset() for invalid PMD LoongArch's huge_pte_offset() currently returns a pointer to a PMD slot even if the underlying entry points to invalid_pte_table (indicating no mapping). Callers like smaps_hugetlb_range() fetch this invalid entry value (the address of invalid_pte_table) via this pointer. The generic is_swap_pte() check then incorrectly identifies this address as a swap entry on LoongArch, because it satisfies the "!pte_present() && !pte_none()" conditions. This misinterpretation, combined with a coincidental match by is_migration_entry() on the address bits, leads to kernel crashes in pfn_swap_entry_to_page(). Fix this at the architecture level by modifying huge_pte_offset() to check the PMD entry's content using pmd_none() before returning. If the entry is invalid (i.e., it points to invalid_pte_table), return NULL instead of the pointer to the slot.

Affected products

Debian Linux: 11.0
Linux kernel: from 5.19 before 6.1.136; from 6.2 before 6.6.89; from 6.7 before 6.12.26; from 6.13 before 6.14.5; 6.15-rc1, 6.15-rc2, 6.15-rc3 — fixed in 6.1.136, 6.12.26, 6.14.5, 6.6.89

How to fix

Upgrade to a fixed version: Linux kernel 6.1.136, 6.12.26, 6.14.5, 6.6.89. Check the vendor advisory for mitigations.

References

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