Skip to content
CVE PROGRAM SOURCE RECORD7.8 High

CVE-2025-38084

mm/hugetlb: unshare page tables during VMA split, not before

Read JSON ↗CVE.org ↗
Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: unshare page tables during VMA split, not before Currently, __split_vma() triggers hugetlb page table unsharing through vm_ops->may_split(). This happens before the VMA lock and rmap locks are taken - which is too early, it allows racing VMA-locked page faults in our process and racing rmap walks from other processes to cause page tables to be shared again before we actually perform the split. Fix it by explicitly calling into the hugetlb unshare logic from __split_vma() in the same place where THP splitting also happens. At that point, both the VMA and the rmap(s) are write-locked. An annoying detail is that we can now call into the helper hugetlb_unshare_pmds() from two different locking contexts: 1. from hugetlb_split(), holding: - mmap lock (exclusively) - VMA lock - file rmap lock (exclusively) 2. hugetlb_unshare_all_pmds(), which I think is designed to be able to call us with only the mmap lock held (in shared mode), but currently only runs while holding mmap lock (exclusively) and VMA lock Backporting note: This commit fixes a racy protection that was introduced in commit b30c14cd6102 ("hugetlb: unshare some PMDs when splitting VMAs"); that commit claimed to fix an issue introduced in 5.13, but it should actually also go all the way back. [jannh@google.com: v2]

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa to < e8847d18cd9fff1edbb45e963d9141273c3b539caffected
  • 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa to < 366298f2b04d2bf1f2f2b7078405bdf9df9bd5d0affected
  • 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa to < 2511ac64bc1617ca716d3ba8464e481a647c1902affected
  • 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa to < af6cfcd0efb7f051af221c418ec8b37a10211947affected
  • 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa to < 9cf5b2a3b72c23fb7b84736d5d19ee6ea718762baffected
  • 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa to < 8a21d5584826f4880f45bbf8f72375f4e6c0ff2aaffected
  • 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa to < 081056dc00a27bccb55ccc3c6f230a3d5fd3f7e0affected

Linux Linux

Default version status: affected

  • 2.6.20affected
  • 0 to < 2.6.20unaffected
  • 5.10.239 to ≤ 5.10.*unaffected
  • 5.15.186 to ≤ 5.15.*unaffected
  • 6.1.142 to ≤ 6.1.*unaffected
  • 6.6.95 to ≤ 6.6.*unaffected
  • 6.12.35 to ≤ 6.12.*unaffected
  • 6.15.4 to ≤ 6.15.*unaffected
  • 6.16 to ≤ *unaffected

References