CVE-2026-93781 (GCVE-0-2026-93781)

Vulnerability from cvelistv5 – Published: 2026-09-24 16:02 – Updated: 2026-09-25 12:42
VLAI
Title
scsi: core: Do not block on tag allocation in scsi_eh_lock_door()
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6e68af666f5336254b5715dca591026b7324499a , < 261c80a6b23e34ba98bcf3f75317e35ecf0a08f0 (git)
Affected: 6e68af666f5336254b5715dca591026b7324499a , < dc9e1b6b9080dd6374cc9a38e4b53abca63c3b1b (git)
Affected: 6e68af666f5336254b5715dca591026b7324499a , < 732cb6bb37fd26863d5786522fb1997e7f5865b4 (git)
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Linux Linux Affected: 2.6.16
Unaffected: 0 , < 2.6.16 (semver)
Unaffected: 6.12.111 , ≤ 6.12.* (semver)
Unaffected: 6.18.53 , ≤ 6.18.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
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              "operator": "OR"
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      "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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T12:42:46.323Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
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          "url": "https://git.kernel.org/stable/c/732cb6bb37fd26863d5786522fb1997e7f5865b4"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-93781",
    "datePublished": "2026-09-24T16:02:13.599Z",
    "dateReserved": "2026-09-18T17:59:28.788Z",
    "dateUpdated": "2026-09-25T12:42:46.323Z",
    "state": "PUBLISHED"
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      "date": "2026-09-27",
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      "percentile": "0.05228"
    },
    "microsoft_vex": {
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      "id": "msrc_CVE-2026-93781",
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      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "scsi: core: Do not block on tag allocation in scsi_eh_lock_door()",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-93781.json",
      "version": "2"
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        "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": [
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "cve": "CVE-2026-93781",
      "id": "CVE-2026-93781",
      "initial_release_date": "2026-09-24T23:48:00Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-93781",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-93781.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.