CVE-2026-72174 (GCVE-0-2026-72174)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:53 – Updated: 2026-08-17 05:09
VLAI
Title
fs/proc/task_mmu: fix hugetlb self-deadlock in pagemap_scan_pte_hole()
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 52526ca7fdb905a768a93f8faa418e9b988fc34b , < a6ac03652d9edc30c2912037ac83beb42cc67f8e (git)
Affected: 52526ca7fdb905a768a93f8faa418e9b988fc34b , < 43b987ed35be9be21a303d1036d4241fec9943df (git)
Affected: 52526ca7fdb905a768a93f8faa418e9b988fc34b , < 18b8a9700610299819d21fd0ea85d24726d17f65 (git)
Affected: 52526ca7fdb905a768a93f8faa418e9b988fc34b , < e92d92bbafb264dc0518d52b846a3c07ed8d523f (git)
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Linux Linux Affected: 6.7
Unaffected: 0 , < 6.7 (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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{
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      "affected": [
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          "product": "Linux",
          "programFiles": [
            "fs/proc/task_mmu.c"
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              "versionType": "semver"
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          "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"
      },
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          "url": "https://git.kernel.org/stable/c/a6ac03652d9edc30c2912037ac83beb42cc67f8e"
        },
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          "url": "https://git.kernel.org/stable/c/43b987ed35be9be21a303d1036d4241fec9943df"
        },
        {
          "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()",
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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"
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        "descriptions": [
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            "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."
          }
        ],
        "id": "CVE-2026-72174",
        "lastModified": "2026-08-17T06:18:17.883",
        "metrics": {},
        "published": "2026-08-15T06:21:35.567",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/18b8a9700610299819d21fd0ea85d24726d17f65"
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          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-19T05:26:38+00:00",
      "cve": "CVE-2026-72174",
      "id": "CVE-2026-72174",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "90",
      "product_status:known_not_affected": "184",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: fs/proc/task_mmu: fix hugetlb self-deadlock in pagemap_scan_pte_hole()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72174.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-15T01:28:31Z",
      "cve": "CVE-2026-72174",
      "id": "CVE-2026-72174",
      "initial_release_date": "2026-09-01T00:52:47Z",
      "product_status:known_affected": "29",
      "product_status:known_not_affected": "333",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-72174",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-72174.json",
      "version": "4"
    }
  }
}



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