GHSA-3F57-G7J5-HJ3Q
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32In 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.
{
"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": "2026-09-13T09:32:29Z",
"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/51a311eb97e91ce1aed3005cb71ccb2e30f8cce8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/557ef547d49ff5e6026a4d39bdd3113bd81d7688"
},
{
"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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