FKIE_CVE-2026-93781

Vulnerability from fkie_nvd - Published: 2026-09-24 17:17 - Updated: 2026-09-25 13:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: scsi: core: Do not block on tag allocation in scsi_eh_lock_door() scsi_eh_lock_door() is called from scsi_restart_operations() while the host is still in the SHOST_RECOVERY state, i.e. before the host is switched back to SHOST_RUNNING and scsi_run_host_queues() restarts the queues. It allocates a request via scsi_alloc_request() with no flags, so blk_mq_get_tag() may block waiting for a free sched tag when all tags are already in use. Those tags can be held by commands that were just requeued by scsi_eh_flush_done_q() during error handling. Such commands cannot be dispatched until the host leaves SHOST_RECOVERY and scsi_run_host_queues() is called - which only happens *after* scsi_eh_lock_door() returns. This forms a circular dependency: - scsi_eh_lock_door(), running in the SCSI error handler thread, waits for a sched tag held by a requeued command; - the requeued command cannot complete and release its sched tag until the error handler thread leaves scsi_restart_operations() and restart the queues. For devices with a single driver tag (e.g. USB storage) it is a guaranteed deadlock and I/O that can never be submitted. This problem has also been reproduced in our environment. Locking the door is a best-effort operation, and scsi_eh_lock_door() already returns silently when the request allocation fails. Pass BLK_MQ_REQ_NOWAIT to scsi_alloc_request() so the allocation fails instead of blocking when no tag is available. This breaks the circular dependency and allows the error handler to finish restarting the queues, after which the pending commands are dispatched normally.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/261c80a6b23e34ba98bcf3f75317e35ecf0a08f0
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/732cb6bb37fd26863d5786522fb1997e7f5865b4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dc9e1b6b9080dd6374cc9a38e4b53abca63c3b1b
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/scsi/scsi_error.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "261c80a6b23e34ba98bcf3f75317e35ecf0a08f0",
              "status": "affected",
              "version": "6e68af666f5336254b5715dca591026b7324499a",
              "versionType": "git"
            },
            {
              "lessThan": "dc9e1b6b9080dd6374cc9a38e4b53abca63c3b1b",
              "status": "affected",
              "version": "6e68af666f5336254b5715dca591026b7324499a",
              "versionType": "git"
            },
            {
              "lessThan": "732cb6bb37fd26863d5786522fb1997e7f5865b4",
              "status": "affected",
              "version": "6e68af666f5336254b5715dca591026b7324499a",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/scsi/scsi_error.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.16"
            },
            {
              "lessThan": "2.6.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "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\nscsi: core: Do not block on tag allocation in scsi_eh_lock_door()\n\nscsi_eh_lock_door() is called from scsi_restart_operations() while the\nhost is still in the SHOST_RECOVERY state, i.e. before the host is\nswitched back to SHOST_RUNNING and scsi_run_host_queues() restarts the\nqueues. It allocates a request via scsi_alloc_request() with no flags,\nso blk_mq_get_tag() may block waiting for a free sched tag when all tags\nare already in use.\n\nThose tags can be held by commands that were just requeued by\nscsi_eh_flush_done_q() during error handling. Such commands cannot be\ndispatched until the host leaves SHOST_RECOVERY and\nscsi_run_host_queues() is called - which only happens *after*\nscsi_eh_lock_door() returns.\n\nThis forms a circular dependency:\n\n  - scsi_eh_lock_door(), running in the SCSI error handler thread, waits\n    for a sched tag held by a requeued command;\n\n  - the requeued command cannot complete and release its sched tag until\n    the error handler thread leaves scsi_restart_operations() and restart\n    the queues.\n\nFor devices with a single driver tag (e.g. USB storage) it is a\nguaranteed deadlock and I/O that can never be submitted. This problem\nhas also been reproduced in our environment.\n\nLocking the door is a best-effort operation, and scsi_eh_lock_door()\nalready returns silently when the request allocation fails. Pass\nBLK_MQ_REQ_NOWAIT to scsi_alloc_request() so the allocation fails\ninstead of blocking when no tag is available. This breaks the circular\ndependency and allows the error handler to finish restarting the queues,\nafter which the pending commands are dispatched normally."
    }
  ],
  "id": "CVE-2026-93781",
  "lastModified": "2026-09-25T13:17:18.617",
  "metrics": {},
  "published": "2026-09-24T17:17:10.670",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/261c80a6b23e34ba98bcf3f75317e35ecf0a08f0"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/732cb6bb37fd26863d5786522fb1997e7f5865b4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dc9e1b6b9080dd6374cc9a38e4b53abca63c3b1b"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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