CVE-2026-93218

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

mm/huge_memory: skip device-private PMDs in madvise_free_huge_pmd

madvise_free_pte_range() checks pmd_trans_huge(*pmd) unlocked, then

madvise_free_huge_pmd() takes pmd_trans_huge_lock(). pmd_is_huge()

returns true for a device-private PMD, so orig_pmd can be device-private

and enter the !pmd_present() branch.

Skip device-private PMDs in that non-present branch and continue to out

before calling pmd_folio(). Downgrade the check to VM_WARN_ON_ONCE() so

an unexpected PMD softleaf logs a warning rather than panicking. Drop the

thp_migration_supported() guard: it expands to

IS_ENABLED(CONFIG_ARCH_SUPPORTS_PMD_SOFTLEAF), and both

pmd_is_migration_entry() and pmd_is_device_private_entry() already return

false when that config is not selected, so the guard suppresses only the

case where the warning would already be silent.

Potential trigger: an HMM-based GPU driver races with madvise(MADV_FREE):

migrate_vma_pages() flips the PMD to a device-private entry between the

caller's pmd_trans_huge() check and the callee's pmd_trans_huge_lock().