FKIE_CVE-2026-74482

Vulnerability from fkie_nvd - Published: 2026-08-15 13:17 - Updated: 2026-08-19 17:21
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/huge_memory: unlock i_mmap_rwsem before releasing after-split folios __folio_split() keeps dereferencing the mapping after the split: shmem_uncharge(mapping->host) and remap_page() while the folios are still frozen/locked, and i_mmap_unlock_read(mapping) at the very end, after the after-split folios have been unlocked and freed. Nothing holds an inode reference across that. The split relies on @folio -- which the beyond-EOF drop loop never removes, as it starts at folio_next(folio) -- staying locked and in the page cache to hold off eviction. But the unlock loop unlocks @folio before i_mmap_unlock_read() runs. If the caller's @lock_at is a tail beyond EOF, as memory_failure() passes when splitting a poisoned tail of a shmem THP that reaches past i_size during truncation, it too is gone from the page cache; so once @folio is unlocked no locked, in-cache folio pins the inode, and a concurrent final iput() can evict and RCU-free it before i_mmap_unlock_read() touches i_mmap_rwsem: BUG: KASAN: slab-use-after-free in __up_read+0x634/0x790 i_mmap_unlock_read include/linux/fs.h:537 [inline] __folio_split+0x732/0x1640 mm/huge_memory.c:4100 try_to_split_thp_page+0xab/0x390 mm/memory-failure.c:1675 memory_failure+0x1394/0x26e0 mm/memory-failure.c:2470 Freed by task 4601: shmem_free_in_core_inode+0x54/0xb0 mm/shmem.c:5177 evict+0x57f/0xac0 fs/inode.c:870 Do every mapping dereference while @folio still pins the inode: drop i_mmap_rwsem right after remap_page(), before the loop that unlocks and frees the after-split folios, and clear @mapping so the exit path does not unlock it again. shmem_uncharge() and remap_page() already run before that point, so after this nothing past the unlock loop touches the inode or the mapping. This is now a rule the split depends on, alongside keeping @folio frozen until the page cache is updated: no inode or mapping dereference once the after-split folios start being unlocked.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/10065fb891651d9541e7a5a2db84c1e656ece4f9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6f5c272d71845a669e4c8ee5c72b376e29a0e6e5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/bc2f5eabaaf60ec18da70b619a8fba1bfb7dea3a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/be106f7855f03d3128ed0ce70ba74b484a90b473
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d640efe94d86d3be893d4c19220362546a637e90
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e3dd774dbfd0b5bc2dbd0995221751b1234f8205
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e923bd21058ea02fd0dcd3549d151d143fd036e5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f87c08060818ebb19bafed37c38244538da25097
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "mm/huge_memory.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "bc2f5eabaaf60ec18da70b619a8fba1bfb7dea3a",
              "status": "affected",
              "version": "baa355fd331424526e742d41d9b90d5f9d10f716",
              "versionType": "git"
            },
            {
              "lessThan": "f87c08060818ebb19bafed37c38244538da25097",
              "status": "affected",
              "version": "baa355fd331424526e742d41d9b90d5f9d10f716",
              "versionType": "git"
            },
            {
              "lessThan": "6f5c272d71845a669e4c8ee5c72b376e29a0e6e5",
              "status": "affected",
              "version": "baa355fd331424526e742d41d9b90d5f9d10f716",
              "versionType": "git"
            },
            {
              "lessThan": "be106f7855f03d3128ed0ce70ba74b484a90b473",
              "status": "affected",
              "version": "baa355fd331424526e742d41d9b90d5f9d10f716",
              "versionType": "git"
            },
            {
              "lessThan": "e3dd774dbfd0b5bc2dbd0995221751b1234f8205",
              "status": "affected",
              "version": "baa355fd331424526e742d41d9b90d5f9d10f716",
              "versionType": "git"
            },
            {
              "lessThan": "10065fb891651d9541e7a5a2db84c1e656ece4f9",
              "status": "affected",
              "version": "baa355fd331424526e742d41d9b90d5f9d10f716",
              "versionType": "git"
            },
            {
              "lessThan": "d640efe94d86d3be893d4c19220362546a637e90",
              "status": "affected",
              "version": "baa355fd331424526e742d41d9b90d5f9d10f716",
              "versionType": "git"
            },
            {
              "lessThan": "e923bd21058ea02fd0dcd3549d151d143fd036e5",
              "status": "affected",
              "version": "baa355fd331424526e742d41d9b90d5f9d10f716",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "mm/huge_memory.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.8"
            },
            {
              "lessThan": "4.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.265",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.216",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.183",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.151",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.103",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.44",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.8",
              "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\nmm/huge_memory: unlock i_mmap_rwsem before releasing after-split folios\n\n__folio_split() keeps dereferencing the mapping after the split:\nshmem_uncharge(mapping-\u003ehost) and remap_page() while the folios are still\nfrozen/locked, and i_mmap_unlock_read(mapping) at the very end, after the\nafter-split folios have been unlocked and freed.\n\nNothing holds an inode reference across that.  The split relies on @folio\n-- which the beyond-EOF drop loop never removes, as it starts at\nfolio_next(folio) -- staying locked and in the page cache to hold off\neviction.  But the unlock loop unlocks @folio before i_mmap_unlock_read()\nruns.  If the caller\u0027s @lock_at is a tail beyond EOF, as memory_failure()\npasses when splitting a poisoned tail of a shmem THP that reaches past\ni_size during truncation, it too is gone from the page cache; so once\n@folio is unlocked no locked, in-cache folio pins the inode, and a\nconcurrent final iput() can evict and RCU-free it before\ni_mmap_unlock_read() touches i_mmap_rwsem:\n\n  BUG: KASAN: slab-use-after-free in __up_read+0x634/0x790\n   i_mmap_unlock_read include/linux/fs.h:537 [inline]\n   __folio_split+0x732/0x1640 mm/huge_memory.c:4100\n   try_to_split_thp_page+0xab/0x390 mm/memory-failure.c:1675\n   memory_failure+0x1394/0x26e0 mm/memory-failure.c:2470\n\n  Freed by task 4601:\n   shmem_free_in_core_inode+0x54/0xb0 mm/shmem.c:5177\n   evict+0x57f/0xac0 fs/inode.c:870\n\nDo every mapping dereference while @folio still pins the inode: drop\ni_mmap_rwsem right after remap_page(), before the loop that unlocks and\nfrees the after-split folios, and clear @mapping so the exit path does not\nunlock it again.  shmem_uncharge() and remap_page() already run before\nthat point, so after this nothing past the unlock loop touches the inode\nor the mapping.\n\nThis is now a rule the split depends on, alongside keeping @folio frozen\nuntil the page cache is updated: no inode or mapping dereference once the\nafter-split folios start being unlocked."
    }
  ],
  "id": "CVE-2026-74482",
  "lastModified": "2026-08-19T17:21:05.477",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-15T13:17:53.053",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/10065fb891651d9541e7a5a2db84c1e656ece4f9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6f5c272d71845a669e4c8ee5c72b376e29a0e6e5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/bc2f5eabaaf60ec18da70b619a8fba1bfb7dea3a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/be106f7855f03d3128ed0ce70ba74b484a90b473"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d640efe94d86d3be893d4c19220362546a637e90"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e3dd774dbfd0b5bc2dbd0995221751b1234f8205"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e923bd21058ea02fd0dcd3549d151d143fd036e5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f87c08060818ebb19bafed37c38244538da25097"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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