FKIE_CVE-2026-45985

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 set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O When allocating blocks during within-EOF DIO and writeback with dioread_nolock enabled, EXT4_GET_BLOCKS_PRE_IO was set to split an existing large unwritten extent. However, EXT4_GET_BLOCKS_CONVERT was set when calling ext4_split_convert_extents(), which may potentially result in stale data issues. Assume we have an unwritten extent, and then DIO writes the second half. [UUUUUUUUUUUUUUUU] on-disk extent U: unwritten extent [UUUUUUUUUUUUUUUU] extent status tree |<- ->| ----> dio write this range First, ext4_iomap_alloc() call ext4_map_blocks() with EXT4_GET_BLOCKS_PRE_IO, EXT4_GET_BLOCKS_UNWRIT_EXT and EXT4_GET_BLOCKS_CREATE flags set. ext4_map_blocks() find this extent and call ext4_split_convert_extents() with EXT4_GET_BLOCKS_CONVERT and the above flags set. Then, ext4_split_convert_extents() calls ext4_split_extent() with EXT4_EXT_MAY_ZEROOUT, EXT4_EXT_MARK_UNWRIT2 and EXT4_EXT_DATA_VALID2 flags set, and it calls ext4_split_extent_at() to split the second half with EXT4_EXT_DATA_VALID2, EXT4_EXT_MARK_UNWRIT1, EXT4_EXT_MAY_ZEROOUT and EXT4_EXT_MARK_UNWRIT2 flags set. However, ext4_split_extent_at() failed to insert extent since a temporary lack -ENOSPC. It zeroes out the first half but convert the entire on-disk extent to written since the EXT4_EXT_DATA_VALID2 flag set, but left the second half as unwritten in the extent status tree. [0000000000SSSSSS] data S: stale data, 0: zeroed [WWWWWWWWWWWWWWWW] on-disk extent W: written extent [WWWWWWWWWWUUUUUU] extent status tree Finally, if the DIO failed to write data to the disk, the stale data in the second half will be exposed once the cached extent entry is gone. Fix this issue by not passing EXT4_GET_BLOCKS_CONVERT when splitting an unwritten extent before submitting I/O, and make ext4_split_convert_extents() to zero out the entire extent range to zero for this case, and also mark the extent in the extent status tree for consistency.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2698731d25823267c29190cb578da9296a0c0d7b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2920ec61c98b9476781359f05b94da84e80f54d4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/37555690f39f78ef69af347d9aff897e07445949
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/67cdb7bd7442bd3cdc6d6088bbb2df9be2fe936c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/716e7439a5a9b18c3ff882c2f8c834b9ced1aaec
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/77e407967cd872cd75d7e4a691908e49c8e6b4d4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/feaf2a80e78f89ee8a3464126077ba8683b62791
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 set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O\n\nWhen allocating blocks during within-EOF DIO and writeback with\ndioread_nolock enabled, EXT4_GET_BLOCKS_PRE_IO was set to split an\nexisting large unwritten extent. However, EXT4_GET_BLOCKS_CONVERT was\nset when calling ext4_split_convert_extents(), which may potentially\nresult in stale data issues.\n\nAssume we have an unwritten extent, and then DIO writes the second 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, ext4_iomap_alloc() call ext4_map_blocks() with\nEXT4_GET_BLOCKS_PRE_IO, EXT4_GET_BLOCKS_UNWRIT_EXT and\nEXT4_GET_BLOCKS_CREATE flags set. ext4_map_blocks() find this extent and\ncall ext4_split_convert_extents() with EXT4_GET_BLOCKS_CONVERT and the\nabove flags set.\n\nThen, ext4_split_convert_extents() calls ext4_split_extent() with\nEXT4_EXT_MAY_ZEROOUT, EXT4_EXT_MARK_UNWRIT2 and EXT4_EXT_DATA_VALID2\nflags set, and it calls ext4_split_extent_at() to split the second half\nwith EXT4_EXT_DATA_VALID2, EXT4_EXT_MARK_UNWRIT1, EXT4_EXT_MAY_ZEROOUT\nand EXT4_EXT_MARK_UNWRIT2 flags set. However, ext4_split_extent_at()\nfailed to insert extent since a temporary lack -ENOSPC. It zeroes out\nthe first half but convert the entire on-disk extent to written since\nthe EXT4_EXT_DATA_VALID2 flag set, but left the second half as unwritten\nin the extent status tree.\n\n   [0000000000SSSSSS]  data                S: stale data, 0: zeroed\n   [WWWWWWWWWWWWWWWW]  on-disk extent      W: written extent\n   [WWWWWWWWWWUUUUUU]  extent status tree\n\nFinally, if the DIO failed to write data to the disk, the stale data in\nthe second half will be exposed once the cached extent entry is gone.\n\nFix this issue by not passing EXT4_GET_BLOCKS_CONVERT when splitting\nan unwritten extent before submitting I/O, and make\next4_split_convert_extents() to zero out the entire extent range\nto zero for this case, and also mark the extent in the extent status\ntree for consistency."
    }
  ],
  "id": "CVE-2026-45985",
  "lastModified": "2026-05-27T14:48:03.013",
  "metrics": {},
  "published": "2026-05-27T14:17:15.820",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2698731d25823267c29190cb578da9296a0c0d7b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2920ec61c98b9476781359f05b94da84e80f54d4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/37555690f39f78ef69af347d9aff897e07445949"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/67cdb7bd7442bd3cdc6d6088bbb2df9be2fe936c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/716e7439a5a9b18c3ff882c2f8c834b9ced1aaec"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/77e407967cd872cd75d7e4a691908e49c8e6b4d4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/feaf2a80e78f89ee8a3464126077ba8683b62791"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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