FKIE_CVE-2026-72174

Vulnerability from fkie_nvd - Published: 2026-08-15 06:21 - Updated: 2026-08-17 06:18
Severity
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
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/18b8a9700610299819d21fd0ea85d24726d17f65
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/43b987ed35be9be21a303d1036d4241fec9943df
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a6ac03652d9edc30c2912037ac83beb42cc67f8e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e92d92bbafb264dc0518d52b846a3c07ed8d523f
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/proc/task_mmu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "a6ac03652d9edc30c2912037ac83beb42cc67f8e",
              "status": "affected",
              "version": "52526ca7fdb905a768a93f8faa418e9b988fc34b",
              "versionType": "git"
            },
            {
              "lessThan": "43b987ed35be9be21a303d1036d4241fec9943df",
              "status": "affected",
              "version": "52526ca7fdb905a768a93f8faa418e9b988fc34b",
              "versionType": "git"
            },
            {
              "lessThan": "18b8a9700610299819d21fd0ea85d24726d17f65",
              "status": "affected",
              "version": "52526ca7fdb905a768a93f8faa418e9b988fc34b",
              "versionType": "git"
            },
            {
              "lessThan": "e92d92bbafb264dc0518d52b846a3c07ed8d523f",
              "status": "affected",
              "version": "52526ca7fdb905a768a93f8faa418e9b988fc34b",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/proc/task_mmu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.7"
            },
            {
              "lessThan": "6.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.97",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.40",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "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."
    }
  ],
  "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"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/43b987ed35be9be21a303d1036d4241fec9943df"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a6ac03652d9edc30c2912037ac83beb42cc67f8e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e92d92bbafb264dc0518d52b846a3c07ed8d523f"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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