CVE-2026-72174 (GCVE-0-2026-72174)
Vulnerability from cvelistv5
Published
2026-08-15 05:53
Modified
2026-08-17 05:09
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
fs/proc/task_mmu: fix hugetlb self-deadlock in pagemap_scan_pte_hole()
A PAGEMAP_SCAN ioctl requesting PM_SCAN_WP_MATCHING on a hugetlb VMA hangs
the calling thread, unkillably, as soon as the scan reaches an unpopulated
part of the range:
do_pagemap_scan()
walk_page_range()
walk_hugetlb_range()
hugetlb_vma_lock_read() # take the vma lock for read ...
pagemap_scan_pte_hole() # ... ->pte_hole() for a hole
uffd_wp_range()
change_protection()
hugetlb_change_protection()
hugetlb_vma_lock_write() # ... and block taking it for write
walk_hugetlb_range() holds the hugetlb vma lock for read across the whole
walk. A present entry goes to ->hugetlb_entry(); an unpopulated one goes
to ->pte_hole(), i.e. pagemap_scan_pte_hole(). To write-protect the hole
that handler calls uffd_wp_range(), which on a hugetlb VMA reaches
hugetlb_change_protection() and takes the same vma lock for write. The
thread then blocks in down_write() waiting for the read lock it is itself
holding.
The populated path avoids this: pagemap_scan_hugetlb_entry()
write-protects the entry inline under the page-table lock and never enters
hugetlb_change_protection().
Do the same for holes. Fault in the page table and install the uffd-wp
marker directly with make_uffd_wp_huge_pte() under the page-table lock,
rather than routing through uffd_wp_range(). That is the same sequence
hugetlb_change_protection() runs for an unpopulated entry, minus the vma
write lock -- which is safe to skip because PMD sharing is disabled on
uffd-wp VMAs (hugetlb_unshare_all_pmds() runs at registration), leaving
nothing for that lock to serialise against.
References
| URL | Tags | |
|---|---|---|
Impacted products
{
"containers": {
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"product": "Linux",
"programFiles": [
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"versions": [
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{
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"version": "6.12.97",
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{
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"version": "6.18.40",
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{
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"version": "7.1.5",
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{
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"version": "7.2",
"versionType": "original_commit_for_fix"
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/proc/task_mmu: fix hugetlb self-deadlock in pagemap_scan_pte_hole()\n\nA PAGEMAP_SCAN ioctl requesting PM_SCAN_WP_MATCHING on a hugetlb VMA hangs\nthe calling thread, unkillably, as soon as the scan reaches an unpopulated\npart of the range:\n\n do_pagemap_scan()\n walk_page_range()\n walk_hugetlb_range()\n hugetlb_vma_lock_read() # take the vma lock for read ...\n pagemap_scan_pte_hole() # ... -\u003epte_hole() for a hole\n uffd_wp_range()\n change_protection()\n hugetlb_change_protection()\n hugetlb_vma_lock_write() # ... and block taking it for write\n\nwalk_hugetlb_range() holds the hugetlb vma lock for read across the whole\nwalk. A present entry goes to -\u003ehugetlb_entry(); an unpopulated one goes\nto -\u003epte_hole(), i.e. pagemap_scan_pte_hole(). To write-protect the hole\nthat handler calls uffd_wp_range(), which on a hugetlb VMA reaches\nhugetlb_change_protection() and takes the same vma lock for write. The\nthread then blocks in down_write() waiting for the read lock it is itself\nholding.\n\nThe populated path avoids this: pagemap_scan_hugetlb_entry()\nwrite-protects the entry inline under the page-table lock and never enters\nhugetlb_change_protection().\n\nDo the same for holes. Fault in the page table and install the uffd-wp\nmarker directly with make_uffd_wp_huge_pte() under the page-table lock,\nrather than routing through uffd_wp_range(). That is the same sequence\nhugetlb_change_protection() runs for an unpopulated entry, minus the vma\nwrite lock -- which is safe to skip because PMD sharing is disabled on\nuffd-wp VMAs (hugetlb_unshare_all_pmds() runs at registration), leaving\nnothing for that lock to serialise against."
}
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"providerMetadata": {
"dateUpdated": "2026-08-17T05:09:36.416Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/a6ac03652d9edc30c2912037ac83beb42cc67f8e"
},
{
"url": "https://git.kernel.org/stable/c/43b987ed35be9be21a303d1036d4241fec9943df"
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{
"url": "https://git.kernel.org/stable/c/18b8a9700610299819d21fd0ea85d24726d17f65"
},
{
"url": "https://git.kernel.org/stable/c/e92d92bbafb264dc0518d52b846a3c07ed8d523f"
}
],
"title": "fs/proc/task_mmu: fix hugetlb self-deadlock in pagemap_scan_pte_hole()",
"x_generator": {
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"cveMetadata": {
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"assignerShortName": "Linux",
"cveId": "CVE-2026-72174",
"datePublished": "2026-08-15T05:53:39.276Z",
"dateReserved": "2026-08-09T03:40:39.910Z",
"dateUpdated": "2026-08-17T05:09:36.416Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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