FKIE_CVE-2026-99254

Vulnerability from fkie_nvd - Published: 2026-11-03 12:17 - Updated: 2026-11-03 20:18
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: io_uring: don't flood a cancelling task with task_work io_ring_exit_work() asks each task which has used the ring to remove its tctx node, by task_work, and repeats that until the list is empty. io_tctx_exit_cb() doesn't touch the node while the task is in io_uring_cancel_generic(), which removes all the nodes at its end. So the work item queues the callback again as soon as it has completed, for nothing. That is more than a waste of time. task_work_run() only returns when it finds the list empty. If the rings are released from inside the cancellation, because requests of other rings held the last references to their files, up to 64 work items keep sending callbacks to the one task which is running them. It never finds the list empty, never gets back to the cancellation, the nodes stay, and so it goes on: a task with 60 pairs of rings which poll each other ran 280000 callbacks in 5 seconds, 20 seconds after exit_group(). It ends when all the senders happen to be late at the same time. Until then the task keeps a CPU and the work items busy. An exiting task can't be killed meanwhile. execve() cancels the requests in the same way, so a live task can get stuck there as well, for minutes. If it takes more than five, the work items run into the WARN_ON_ONCE(time_after(jiffies, timeout)) of io_ring_exit_work(). No privilege is needed for any of this. If the callback has met a task in cancellation, wait a little before it is sent again. Nobody has to wake the work item up for that: either the node is gone by then, or it is the turn of the next round.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/22e643e61b9b6299b42ff7d88bab48bccada8a5d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/61c761fc21e00e45c33c2bb596be442d92fb8792
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a22fb44e988b01b82235ea07f0bf0fc73e256596
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/abdc57c7ebabaaf0b622178a6a85834e1e54ff80
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "io_uring/io_uring.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "a22fb44e988b01b82235ea07f0bf0fc73e256596",
              "status": "affected",
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "versionType": "git"
            },
            {
              "lessThan": "2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1",
              "status": "affected",
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "versionType": "git"
            },
            {
              "lessThan": "61c761fc21e00e45c33c2bb596be442d92fb8792",
              "status": "affected",
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "versionType": "git"
            },
            {
              "lessThan": "14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9",
              "status": "affected",
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "versionType": "git"
            },
            {
              "lessThan": "abdc57c7ebabaaf0b622178a6a85834e1e54ff80",
              "status": "affected",
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "versionType": "git"
            },
            {
              "lessThan": "22e643e61b9b6299b42ff7d88bab48bccada8a5d",
              "status": "affected",
              "version": "d56d938b4bef3e1421a42023cdcd6e13c1f50831",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "io_uring/io_uring.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.12"
            },
            {
              "lessThan": "5.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.191",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.161",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.115",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.60",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.14",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.4-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring: don\u0027t flood a cancelling task with task_work\n\nio_ring_exit_work() asks each task which has used the ring to remove its\ntctx node, by task_work, and repeats that until the list is empty.\nio_tctx_exit_cb() doesn\u0027t touch the node while the task is in\nio_uring_cancel_generic(), which removes all the nodes at its end. So the\nwork item queues the callback again as soon as it has completed, for\nnothing.\n\nThat is more than a waste of time. task_work_run() only returns when it\nfinds the list empty. If the rings are released from inside the\ncancellation, because requests of other rings held the last references to\ntheir files, up to 64 work items keep sending callbacks to the one task\nwhich is running them. It never finds the list empty, never gets back to\nthe cancellation, the nodes stay, and so it goes on: a task with 60 pairs\nof rings which poll each other ran 280000 callbacks in 5 seconds, 20\nseconds after exit_group(). It ends when all the senders happen to be late\nat the same time. Until then the task keeps a CPU and the work items busy.\n\nAn exiting task can\u0027t be killed meanwhile. execve() cancels the requests in\nthe same way, so a live task can get stuck there as well, for minutes. If\nit takes more than five, the work items run into the\nWARN_ON_ONCE(time_after(jiffies, timeout)) of io_ring_exit_work(). No\nprivilege is needed for any of this.\n\nIf the callback has met a task in cancellation, wait a little before it is\nsent again. Nobody has to wake the work item up for that: either the node\nis gone by then, or it is the turn of the next round."
    }
  ],
  "id": "CVE-2026-99254",
  "lastModified": "2026-11-03T20:18:31.393",
  "metrics": {},
  "published": "2026-11-03T12:17:32.137",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/22e643e61b9b6299b42ff7d88bab48bccada8a5d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/61c761fc21e00e45c33c2bb596be442d92fb8792"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a22fb44e988b01b82235ea07f0bf0fc73e256596"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/abdc57c7ebabaaf0b622178a6a85834e1e54ff80"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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