{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "728cbac5fe219d3b8a21a0688a08f2b7f8aeda2b"
            },
            {
              "fixed": "7dd26adf7e7d482af524e3a0cca4a81ef7c159d0"
            },
            {
              "fixed": "8f188dd11a1c2ad94caeaee36ef68bb8221d4a12"
            },
            {
              "fixed": "432a9b2780c0a01caf547bd1fc2fcf28aeb8d173"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "42ea64e01c96e594fb4f80c54dfe4f934d008a6e"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "6.14.6"
            },
            {
              "fixed": "6.15"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.15.0"
            },
            {
              "fixed": "6.18.42"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.1.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68173.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nublk: wait on ublk_dev_ready() instead of ub-\u003ecompletion\n\nub-\u003ecompletion is only re-armed by a successful START_USER_RECOVERY. If\nthe ublk server sends END_USER_RECOVERY without one - e.g. its START\nfailed with -EBUSY and the error was ignored - the wait is satisfied by\nthe stale completion of the previous recovery cycle, and the device is\nmarked LIVE and the requeue list kicked while the FETCH stream is still\nrunning and ubq-\u003ecanceling is still set. The kick redispatches a\npreviously requeued request, __ublk_queue_rq_common() sees -\u003ecanceling\nand parks it again via __ublk_abort_rq(), and after the last FETCH\nclears -\u003ecanceling nothing ever kicks the requeue list again: the\nrequest is stranded there while holding its tag. If it is the flush\nmachinery's flush_rq, every subsequent fsync piles up in uninterruptible\nsleep and teardown hangs on tag draining. This matches a report of a\nlost PREFLUSH with ext4 on top of ublk after daemon crash recovery.\n\nub-\u003ecompletion is an edge-triggered latch used as a proxy for the level\ncondition \"every queue has fetched all I/O commands\", which can regress\n(F_BATCH's UNPREP, daemon death) and whose re-arm can be skipped. Drop\nit and wait on the real condition instead: the new helper\nublk_wait_dev_ready_and_lock() waits on ublk_dev_ready() via\nwait_var_event_interruptible(), woken from ublk_mark_io_ready(), then\nre-checks it under ub-\u003emutex, waiting again on regression, and returns\nwith the mutex held and readiness guaranteed.\n\nReadiness becomes true in the same ub-\u003emutex critical section that\nclears the last queue's -\u003ecanceling, so END_USER_RECOVERY marks the\ndevice LIVE and kicks the requeue list strictly after -\u003ecanceling\nclears. The wait stays interruptible, so a server whose daemon died can\nstill be signalled out. For ublk_ctrl_start_dev() this replaces the\nfail-fast -EINVAL on an F_BATCH ready-\u003eUNPREP regression with waiting\nuntil the device is ready again.",
  "id": "CVE-2026-68173",
  "modified": "2026-08-15T11:31:16.954899856Z",
  "published": "2026-08-10T11:59:42.889Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/432a9b2780c0a01caf547bd1fc2fcf28aeb8d173"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7dd26adf7e7d482af524e3a0cca4a81ef7c159d0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8f188dd11a1c2ad94caeaee36ef68bb8221d4a12"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68173.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68173"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ublk: wait on ublk_dev_ready() instead of ub-\u003ecompletion"
}