CVE-2026-90183 (GCVE-0-2026-90183)
Vulnerability from cvelistv5
Published
2026-09-17 16:07
Modified
2026-10-21 12:50
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: blk-iolatency: clear delay state when freeing policy data io.latency can throttle a group which has no latency target of its own. When a sibling misses its target, check_scale_change() scales down its peers, and a peer that reaches queue depth one gets blkcg_use_delay() called on it on every further scale-down, even with min_lat_nsec == 0. iolatency_pd_offline() resets the target through iolatency_set_min_lat_nsec(), which clears the delay only on a nonzero to zero transition, so it never clears such a peer. Freeing the policy data then leaves blkg->use_delay set and blkcg->congestion_count elevated with nothing left that can drop it. blk_cgroup_congested() then returns true for every task in that cgroup and its descendants for as long as the cgroup lives: page_cache_sync_ra() cuts readahead to a single page, page_cache_async_ra() skips it altogether, and __folio_throttle_swaprate() takes swap_avail_lock and schedules a throttle on anonymous folio allocation. Clear the delay in iolatency_pd_free(). By then bio-held blkg references have drained, or the queue is frozen for policy deactivation, so check_scale_change() cannot re-arm it. The free callback can also see policy data which was never attached to a blkg, hence the pd->blkg check.
References
Impacted products
Vendor Product Version
Linux Linux Version: d70675121546c35feaceebf7ed9caed8716640f3
Version: d70675121546c35feaceebf7ed9caed8716640f3
Version: d70675121546c35feaceebf7ed9caed8716640f3
Version: d70675121546c35feaceebf7ed9caed8716640f3
Version: d70675121546c35feaceebf7ed9caed8716640f3
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{
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblk-iolatency: clear delay state when freeing policy data\n\nio.latency can throttle a group which has no latency target of its own.\nWhen a sibling misses its target, check_scale_change() scales down its\npeers, and a peer that reaches queue depth one gets blkcg_use_delay()\ncalled on it on every further scale-down, even with min_lat_nsec == 0.\n\niolatency_pd_offline() resets the target through\niolatency_set_min_lat_nsec(), which clears the delay only on a nonzero\nto zero transition, so it never clears such a peer.  Freeing the policy\ndata then leaves blkg-\u003euse_delay set and blkcg-\u003econgestion_count\nelevated with nothing left that can drop it.\n\nblk_cgroup_congested() then returns true for every task in that cgroup\nand its descendants for as long as the cgroup lives: page_cache_sync_ra()\ncuts readahead to a single page, page_cache_async_ra() skips it\naltogether, and __folio_throttle_swaprate() takes swap_avail_lock and\nschedules a throttle on anonymous folio allocation.\n\nClear the delay in iolatency_pd_free().  By then bio-held blkg\nreferences have drained, or the queue is frozen for policy\ndeactivation, so check_scale_change() cannot re-arm it.  The free\ncallback can also see policy data which was never attached to a blkg,\nhence the pd-\u003eblkg check."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:50:22.454Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/53ccb4b967edc5f82ff6f9c066fb96c31aa7561a"
        },
        {
          "url": "https://git.kernel.org/stable/c/b6449a915d1826e1450f6368fc379fe44caa06ca"
        },
        {
          "url": "https://git.kernel.org/stable/c/5c6593422eb3c3a21505436ccf74599a433584c8"
        },
        {
          "url": "https://git.kernel.org/stable/c/02f1b90ab33ef99c89dd96a385b432ff57abc64d"
        },
        {
          "url": "https://git.kernel.org/stable/c/8935bf22c0a0db517a7f72f7097300e05dd852f5"
        }
      ],
      "title": "blk-iolatency: clear delay state when freeing policy data",
      "x_generator": {
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90183",
    "datePublished": "2026-09-17T16:07:07.045Z",
    "dateReserved": "2026-09-11T19:38:34.791Z",
    "dateUpdated": "2026-10-21T12:50:22.454Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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