FKIE_CVE-2026-45858

Vulnerability from fkie_nvd - Published: 2026-05-27 14:16 - Updated: 2026-05-27 14:48
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: ext4: don't zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1 When allocating initialized blocks from a large unwritten extent, or when splitting an unwritten extent during end I/O and converting it to initialized, there is currently a potential issue of stale data if the extent needs to be split in the middle. 0 A B N [UUUUUUUUUUUU] U: unwritten extent [--DDDDDDDD--] D: valid data |<- ->| ----> this range needs to be initialized ext4_split_extent() first try to split this extent at B with EXT4_EXT_DATA_ENTIRE_VALID1 and EXT4_EXT_MAY_ZEROOUT flag set, but ext4_split_extent_at() failed to split this extent due to temporary lack of space. It zeroout B to N and mark the entire extent from 0 to N as written. 0 A B N [WWWWWWWWWWWW] W: written extent [SSDDDDDDDDZZ] Z: zeroed, S: stale data ext4_split_extent() then try to split this extent at A with EXT4_EXT_DATA_VALID2 flag set. This time, it split successfully and left a stale written extent from 0 to A. 0 A B N [WW|WWWWWWWWWW] [SS|DDDDDDDDZZ] Fix this by pass EXT4_EXT_DATA_PARTIAL_VALID1 to ext4_split_extent_at() when splitting at B, don't convert the entire extent to written and left it as unwritten after zeroing out B to N. The remaining work is just like the standard two-part split. ext4_split_extent() will pass the EXT4_EXT_DATA_VALID2 flag when it calls ext4_split_extent_at() for the second time, allowing it to properly handle the split. If the split is successful, it will keep extent from 0 to A as unwritten.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1bf6974822d1dba86cf11b5f05498581cf3488a2
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/58ddae5d77b1db3a27b891c75a8fa120239ac092
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7015fcf473796e1d2d876f241bd9e0c36f3d4eef
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d17857b4fb9ba5745b59be0ef38fd532991fccbf
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d67c8ecf3d8fda9b8ef80e6f665d84b6d6ac9d88
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 zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1\n\nWhen allocating initialized blocks from a large unwritten extent, or\nwhen splitting an unwritten extent during end I/O and converting it to\ninitialized, there is currently a potential issue of stale data if the\nextent needs to be split in the middle.\n\n       0  A      B  N\n       [UUUUUUUUUUUU]    U: unwritten extent\n       [--DDDDDDDD--]    D: valid data\n          |\u003c-  -\u003e| ----\u003e this range needs to be initialized\n\next4_split_extent() first try to split this extent at B with\nEXT4_EXT_DATA_ENTIRE_VALID1 and EXT4_EXT_MAY_ZEROOUT flag set, but\next4_split_extent_at() failed to split this extent due to temporary lack\nof space. It zeroout B to N and mark the entire extent from 0 to N\nas written.\n\n       0  A      B  N\n       [WWWWWWWWWWWW]    W: written extent\n       [SSDDDDDDDDZZ]    Z: zeroed, S: stale data\n\next4_split_extent() then try to split this extent at A with\nEXT4_EXT_DATA_VALID2 flag set. This time, it split successfully and left\na stale written extent from 0 to A.\n\n       0  A      B   N\n       [WW|WWWWWWWWWW]\n       [SS|DDDDDDDDZZ]\n\nFix this by pass EXT4_EXT_DATA_PARTIAL_VALID1 to ext4_split_extent_at()\nwhen splitting at B, don\u0027t convert the entire extent to written and left\nit as unwritten after zeroing out B to N. The remaining work is just\nlike the standard two-part split. ext4_split_extent() will pass the\nEXT4_EXT_DATA_VALID2 flag when it calls ext4_split_extent_at() for the\nsecond time, allowing it to properly handle the split. If the split is\nsuccessful, it will keep extent from 0 to A as unwritten."
    }
  ],
  "id": "CVE-2026-45858",
  "lastModified": "2026-05-27T14:48:31.480",
  "metrics": {},
  "published": "2026-05-27T14:16:57.943",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1bf6974822d1dba86cf11b5f05498581cf3488a2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/58ddae5d77b1db3a27b891c75a8fa120239ac092"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7015fcf473796e1d2d876f241bd9e0c36f3d4eef"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d17857b4fb9ba5745b59be0ef38fd532991fccbf"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d67c8ecf3d8fda9b8ef80e6f665d84b6d6ac9d88"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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