CVE-2026-98538 (GCVE-0-2026-98538)
Vulnerability from cvelistv5
Published
2026-10-18 15:18
Modified
2026-10-19 09:21
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes cleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes per call and is called again until the dying wb is drained, but every call walks wb->b_attached and then wb->b_dirty_time from the same end. Inodes already prepared (they stay on the list with I_WB_SWITCH set until the switch worker runs) and inodes that cannot be switched (I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb) stay where they are, so each pass rescans a growing run of them under wb->list_lock and a full drain is quadratic in the number of inodes on the list. With ~17M inodes attached to one dying cgwb we saw this end in soft lockups, with CPUs reported stuck for 21-48s. Walk both lists from the oldest end and move every scanned inode to the newest end, so the next pass starts where the previous one stopped and the drain becomes linear. b_attached is unordered, so nobody sees the reorder there. b_dirty_time is ordered by dirtied_when, but the oldest unscanned inode stays at the end move_expired_inodes() picks from, sync takes the whole list regardless of order, and prepared inodes leave the list as soon as the switch work runs and get a new dirtied_time_when on the new wb anyway, so the only inodes left out of order are the ones that can never switch (DAX), and only on the dying wb.
References
Impacted products
Vendor Product Version
Linux Linux Version: c22d70a162d3cc177282c4487be4d54876ca55c8
Version: c22d70a162d3cc177282c4487be4d54876ca55c8
Version: c22d70a162d3cc177282c4487be4d54876ca55c8
Version: c22d70a162d3cc177282c4487be4d54876ca55c8
Version: c22d70a162d3cc177282c4487be4d54876ca55c8
Version: c22d70a162d3cc177282c4487be4d54876ca55c8
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{
  "containers": {
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          "programFiles": [
            "fs/fs-writeback.c"
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nwriteback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes\n\ncleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes\nper call and is called again until the dying wb is drained, but every\ncall walks wb-\u003eb_attached and then wb-\u003eb_dirty_time from the same end.\nInodes already prepared (they stay on the list with I_WB_SWITCH set\nuntil the switch worker runs) and inodes that cannot be switched\n(I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb)\nstay where they are, so each pass rescans a growing run of them under\nwb-\u003elist_lock and a full drain is quadratic in the number of inodes on\nthe list. With ~17M inodes attached to one dying cgwb we saw this end\nin soft lockups, with CPUs reported stuck for 21-48s.\n\nWalk both lists from the oldest end and move every scanned inode to\nthe newest end, so the next pass starts where the previous one stopped\nand the drain becomes linear. b_attached is unordered, so nobody sees\nthe reorder there. b_dirty_time is ordered by dirtied_when, but the\noldest unscanned inode stays at the end move_expired_inodes() picks\nfrom, sync takes the whole list regardless of order, and prepared\ninodes leave the list as soon as the switch work runs and get a new\ndirtied_time_when on the new wb anyway, so the only inodes left out of\norder are the ones that can never switch (DAX), and only on the dying\nwb."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:21:21.678Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2d1da58c79b66646721a644c6eb4dd1f9c5c9327"
        },
        {
          "url": "https://git.kernel.org/stable/c/c96b4d1628868e1195da1a896f79e06f350a3187"
        },
        {
          "url": "https://git.kernel.org/stable/c/624dd0931162523d70f9db8c120b5ec6429a9b97"
        },
        {
          "url": "https://git.kernel.org/stable/c/dd4b92067238771b604b59fdda8efed6d70ee823"
        },
        {
          "url": "https://git.kernel.org/stable/c/9dac137bf77e0683778fb34c86e730c6129e8cb6"
        },
        {
          "url": "https://git.kernel.org/stable/c/f6988c90671e83db79df1b7b9d6fdb0e5947fd84"
        }
      ],
      "title": "writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes",
      "x_generator": {
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98538",
    "datePublished": "2026-10-18T15:18:05.901Z",
    "dateReserved": "2026-09-25T10:25:14.356Z",
    "dateUpdated": "2026-10-19T09:21:21.678Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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