mm/hugetlb: unshare page tables during VMA split, not before
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]
CVE-2025-38084
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2025-38084
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa",
"lessThan": "e8847d18cd9fff1edbb45e963d9141273c3b539c",
"versionType": "git"
},
{
"status": "affected",
"version": "39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa",
"lessThan": "366298f2b04d2bf1f2f2b7078405bdf9df9bd5d0",
"versionType": "git"
},
{
"status": "affected",
"version": "39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa",
"lessThan": "2511ac64bc1617ca716d3ba8464e481a647c1902",
"versionType": "git"
},
{
"status": "affected",
"version": "39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa",
"lessThan": "af6cfcd0efb7f051af221c418ec8b37a10211947",
"versionType": "git"
},
{
"status": "affected",
"version": "39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa",
"lessThan": "9cf5b2a3b72c23fb7b84736d5d19ee6ea718762b",
"versionType": "git"
},
{
"status": "affected",
"version": "39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa",
"lessThan": "8a21d5584826f4880f45bbf8f72375f4e6c0ff2a",
"versionType": "git"
},
{
"status": "affected",
"version": "39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa",
"lessThan": "081056dc00a27bccb55ccc3c6f230a3d5fd3f7e0",
"versionType": "git"
}
],
"programFiles": [
"include/linux/hugetlb.h",
"mm/hugetlb.c",
"mm/vma.c",
"tools/testing/vma/vma_internal.h"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.20"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.20",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.239",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.186",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.142",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.95",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.35",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.15.4",
"versionType": "semver",
"lessThanOrEqual": "6.15.*"
},
{
"status": "unaffected",
"version": "6.16",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"include/linux/hugetlb.h",
"mm/hugetlb.c",
"mm/vma.c",
"tools/testing/vma/vma_internal.h"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2025-38084
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #30515 · Revision 1
- Added to Heist Feed
- Publisher date