GHSA-3F57-G7J5-HJ3Q

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-10-30 15:33
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed

In polled-VBUS mode (board.vbus_pin && board.vbus_polled), probe arms a self-restarting cycle: at91_vbus_timer() schedules vbus_timer_work, and at91_vbus_timer_work() calls at91_vbus_update() and re-arms the timer via mod_timer(). Both recover the same udc through container_of and dereference it on every iteration.

Neither teardown path cancels this cycle. udc is devm-allocated, so it is freed after at91udc_remove() returns, and is likewise freed when probe fails and devres runs. A timer callback or work item that is pending or running at either point dereferences the freed udc.

Add at91_udc_shutdown_vbus_timer() and call it from at91udc_remove() and from the usb_add_gadget_udc() failure path in probe; the remaining probe error paths fail before the timer is armed. timer_shutdown_sync() waits for a running callback and clears timer->function, which makes the work handler's mod_timer() a permanent no-op; cancel_work_sync() then drains any pending or running work whose re-arm attempt now does nothing. The timer must be shut down first, since cancelling the work alone would let the timer re-queue it. The guard mirrors probe: in IRQ mode the timer and work_struct are never initialized.

This does not require a fault; a normal driver unbind can interleave with an already queued work item.

This issue was found by an in-house static analysis tool.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-89738"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:20:04Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed\n\nIn polled-VBUS mode (board.vbus_pin \u0026\u0026 board.vbus_polled), probe arms a\nself-restarting cycle: at91_vbus_timer() schedules vbus_timer_work, and\nat91_vbus_timer_work() calls at91_vbus_update() and re-arms the timer via\nmod_timer(). Both recover the same udc through container_of and dereference\nit on every iteration.\n\nNeither teardown path cancels this cycle. udc is devm-allocated, so it is\nfreed after at91udc_remove() returns, and is likewise freed when probe\nfails and devres runs. A timer callback or work item that is pending or\nrunning at either point dereferences the freed udc.\n\nAdd at91_udc_shutdown_vbus_timer() and call it from at91udc_remove() and\nfrom the usb_add_gadget_udc() failure path in probe; the remaining probe\nerror paths fail before the timer is armed. timer_shutdown_sync() waits\nfor a running callback and clears timer-\u003efunction, which makes the work\nhandler\u0027s mod_timer() a permanent no-op; cancel_work_sync() then drains\nany pending or running work whose re-arm attempt now does nothing. The\ntimer must be shut down first, since cancelling the work alone would let\nthe timer re-queue it. The guard mirrors probe: in IRQ mode the timer and\nwork_struct are never initialized.\n\nThis does not require a fault; a normal driver unbind can interleave with\nan already queued work item.\n\nThis issue was found by an in-house static analysis tool.",
  "id": "GHSA-3f57-g7j5-hj3q",
  "modified": "2026-10-30T15:33:24Z",
  "published": "2026-09-11T21:31:38Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89738"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1674e34fe61ad3f5585dc833ba6bb6522912e6a5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2440ce54b8c4c8aa6963c181eb56164a466fbe1c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/51a311eb97e91ce1aed3005cb71ccb2e30f8cce8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/557ef547d49ff5e6026a4d39bdd3113bd81d7688"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/723d73b245843d4fff4c3f42e857c78c2b2d414e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a2a602cb1e28d76a5398cec3fa21b0110385f501"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c27d13ce4bab80fbdf6523928071b6c24b37606c"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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