GHSA-G824-Q393-34QQ
Vulnerability from github – Published: 2026-09-04 18:31 – Updated: 2026-09-04 18:31In 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.
{
"affected": [],
"aliases": [
"CVE-2026-80854"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-04T16:18:14Z",
"severity": null
},
"details": "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.",
"id": "GHSA-g824-q393-34qq",
"modified": "2026-09-04T18:31:29Z",
"published": "2026-09-04T18:31:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80854"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/178f59a0bccd3f66cdfa5184310f31a58b7257c4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2efbfd42441d3ef8137aff2d59e9835e1d5ae780"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/85aa61fedcb4eb13f3dc5db73f6dc359f41f5d95"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ad6f0375d2e93a1d8c015463e5e92dfcb26e311b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bbd6aa311a9f4dd17822c7557451458d3d2e980b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c1f359d9a5efed458946063de65ddbeaacc4f165"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c39d0916da47d94909391876c9e5bd429ea7b1b9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c494c5562ca69b61a82f566e3b87a445d2c28929"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/eaa96a8458f54d6cf0954242ab8b1df2a6fccafa"
}
],
"schema_version": "1.4.0",
"severity": []
}
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