CVE-2026-80854 (GCVE-0-2026-80854)
Vulnerability from cvelistv5
Published
2026-09-04 15:55
Modified
2026-09-04 15:55
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_tcm: keep port count until LUN teardown completes tcm_usbg_drop_nexus() permits session removal once tpg_port_count reaches zero. However, usbg_port_unlink() currently decrements that count from the fabric_pre_unlink() callback, before core_dev_del_lun() waits for active se_lun references to drain. If removal of the last LUN races a nexus removal, the latter can observe a zero port count and call target_remove_session(). This frees sess_cmd_map while an in-flight struct usbg_cmd, including its work item, can still be accessed. Overlapping the last-LUN unlink with nexus removal reproduces this lifetime violation as a DEBUG_OBJECTS "free active" warning for usbg_cmd_work, followed by a target-core BUG/Oops. The generic target-core unlink path has no callback after core_dev_del_lun() completes. Add an optional fabric_post_unlink() callback and use it for the f_tcm port count. The count now remains nonzero until core_dev_del_lun() has finished draining active LUN references, preventing nexus removal from freeing the session during command completion.
References
Impacted products
Vendor Product Version
Linux Linux Version: c52661d60f636d17e26ad834457db333bd1df494
Version: c52661d60f636d17e26ad834457db333bd1df494
Version: c52661d60f636d17e26ad834457db333bd1df494
Version: c52661d60f636d17e26ad834457db333bd1df494
Version: c52661d60f636d17e26ad834457db333bd1df494
Version: c52661d60f636d17e26ad834457db333bd1df494
Version: c52661d60f636d17e26ad834457db333bd1df494
Version: c52661d60f636d17e26ad834457db333bd1df494
Version: c52661d60f636d17e26ad834457db333bd1df494
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{
  "containers": {
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/target/target_core_fabric_configfs.c",
            "drivers/usb/gadget/function/f_tcm.c",
            "include/target/target_core_fabric.h"
          ],
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          "vendor": "Linux",
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          "programFiles": [
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            "drivers/usb/gadget/function/f_tcm.c",
            "include/target/target_core_fabric.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "3.5"
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              "version": "0",
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              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_tcm: keep port count until LUN teardown completes\n\ntcm_usbg_drop_nexus() permits session removal once tpg_port_count\nreaches zero. However, usbg_port_unlink() currently decrements that\ncount from the fabric_pre_unlink() callback, before core_dev_del_lun()\nwaits for active se_lun references to drain.\n\nIf removal of the last LUN races a nexus removal, the latter can observe\na zero port count and call target_remove_session(). This frees\nsess_cmd_map while an in-flight struct usbg_cmd, including its work item,\ncan still be accessed.\n\nOverlapping the last-LUN unlink with nexus removal reproduces this\nlifetime violation as a DEBUG_OBJECTS \"free active\" warning for\nusbg_cmd_work, followed by a target-core BUG/Oops.\n\nThe generic target-core unlink path has no callback after\ncore_dev_del_lun() completes. Add an optional fabric_post_unlink()\ncallback and use it for the f_tcm port count. The count now remains\nnonzero until core_dev_del_lun() has finished draining active LUN\nreferences, preventing nexus removal from freeing the session during\ncommand completion."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-04T15:55:06.478Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/c494c5562ca69b61a82f566e3b87a445d2c28929"
        },
        {
          "url": "https://git.kernel.org/stable/c/c1f359d9a5efed458946063de65ddbeaacc4f165"
        },
        {
          "url": "https://git.kernel.org/stable/c/178f59a0bccd3f66cdfa5184310f31a58b7257c4"
        },
        {
          "url": "https://git.kernel.org/stable/c/ad6f0375d2e93a1d8c015463e5e92dfcb26e311b"
        },
        {
          "url": "https://git.kernel.org/stable/c/2efbfd42441d3ef8137aff2d59e9835e1d5ae780"
        },
        {
          "url": "https://git.kernel.org/stable/c/85aa61fedcb4eb13f3dc5db73f6dc359f41f5d95"
        },
        {
          "url": "https://git.kernel.org/stable/c/bbd6aa311a9f4dd17822c7557451458d3d2e980b"
        },
        {
          "url": "https://git.kernel.org/stable/c/eaa96a8458f54d6cf0954242ab8b1df2a6fccafa"
        },
        {
          "url": "https://git.kernel.org/stable/c/c39d0916da47d94909391876c9e5bd429ea7b1b9"
        }
      ],
      "title": "usb: gadget: f_tcm: keep port count until LUN teardown completes",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80854",
    "datePublished": "2026-09-04T15:55:06.478Z",
    "dateReserved": "2026-08-26T14:34:25.797Z",
    "dateUpdated": "2026-09-04T15:55:06.478Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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