FKIE_CVE-2026-45912

Vulnerability from fkie_nvd - Published: 2026-05-27 14:17 - Updated: 2026-05-27 14:48
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: ext4: don't cache extent during splitting extent Caching extents during the splitting process is risky, as it may result in stale extents remaining in the status tree. Moreover, in most cases, the corresponding extent block entries are likely already cached before the split happens, making caching here not particularly useful. Assume we have an unwritten extent, and then DIO writes the first half. [UUUUUUUUUUUUUUUU] on-disk extent U: unwritten extent [UUUUUUUUUUUUUUUU] extent status tree |<- ->| ----> dio write this range First, when ext4_split_extent_at() splits this extent, it truncates the existing extent and then inserts a new one. During this process, this extent status entry may be shrunk, and calls to ext4_find_extent() and ext4_cache_extents() may occur, which could potentially insert the truncated range as a hole into the extent status tree. After the split is completed, this hole is not replaced with the correct status. [UUUUUUU|UUUUUUUU] on-disk extent U: unwritten extent [UUUUUUU|HHHHHHHH] extent status tree H: hole Then, the outer calling functions will not correct this remaining hole extent either. Finally, if we perform a delayed buffer write on this latter part, it will re-insert the delayed extent and cause an error in space accounting. In adition, if the unwritten extent cache is not shrunk during the splitting, ext4_cache_extents() also conflicts with existing extents when caching extents. In the future, we will add checks when caching extents, which will trigger a warning. Therefore, Do not cache extents that are being split.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4c2d9dac4d328244f9365b0a1fa27ec802821820
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5b1f4290453314e11cd8e15c7baa8a9b76c19b23
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/692103feca376ae4298c92aa8828015d20f1d87b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8302b5b4aacdbb378f7b1216bb2ee782b5142415
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8b4b19a2f96348d70bfa306ef7d4a13b0bcbea79
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/93b2ebbbcb2e63cfc21a1946dfe91d3aa7952036
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/96007fd3c106aea773c1afae2d6f64cceb6da208
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9a2b95cdaf07785e2739199037bd9c0863ccc1be
Impacted products
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: don\u0027t cache extent during splitting extent\n\nCaching extents during the splitting process is risky, as it may result\nin stale extents remaining in the status tree. Moreover, in most cases,\nthe corresponding extent block entries are likely already cached before\nthe split happens, making caching here not particularly useful.\n\nAssume we have an unwritten extent, and then DIO writes the first half.\n\n  [UUUUUUUUUUUUUUUU] on-disk extent        U: unwritten extent\n  [UUUUUUUUUUUUUUUU] extent status tree\n  |\u003c-   -\u003e| ----\u003e dio write this range\n\nFirst, when ext4_split_extent_at() splits this extent, it truncates the\nexisting extent and then inserts a new one. During this process, this\nextent status entry may be shrunk, and calls to ext4_find_extent() and\next4_cache_extents() may occur, which could potentially insert the\ntruncated range as a hole into the extent status tree. After the split\nis completed, this hole is not replaced with the correct status.\n\n  [UUUUUUU|UUUUUUUU] on-disk extent        U: unwritten extent\n  [UUUUUUU|HHHHHHHH] extent status tree    H: hole\n\nThen, the outer calling functions will not correct this remaining hole\nextent either. Finally, if we perform a delayed buffer write on this\nlatter part, it will re-insert the delayed extent and cause an error in\nspace accounting.\n\nIn adition, if the unwritten extent cache is not shrunk during the\nsplitting, ext4_cache_extents() also conflicts with existing extents\nwhen caching extents. In the future, we will add checks when caching\nextents, which will trigger a warning. Therefore, Do not cache extents\nthat are being split."
    }
  ],
  "id": "CVE-2026-45912",
  "lastModified": "2026-05-27T14:48:03.013",
  "metrics": {},
  "published": "2026-05-27T14:17:05.867",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4c2d9dac4d328244f9365b0a1fa27ec802821820"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5b1f4290453314e11cd8e15c7baa8a9b76c19b23"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/692103feca376ae4298c92aa8828015d20f1d87b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8302b5b4aacdbb378f7b1216bb2ee782b5142415"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8b4b19a2f96348d70bfa306ef7d4a13b0bcbea79"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/93b2ebbbcb2e63cfc21a1946dfe91d3aa7952036"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/96007fd3c106aea773c1afae2d6f64cceb6da208"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9a2b95cdaf07785e2739199037bd9c0863ccc1be"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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