UBUNTU-CVE-2026-64583: Use After Free
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: udc: bdc: free IRQ and drain funcwakenotify before teardown The Broadcom BDC UDC driver registers its IRQ handler with devmrequestirq() in bdcudcinit(), so the IRQ is released by devm only after bdcremove() returns. devm releases resources in reverse LIFO order, but bdcremove() runs bdcudcexit() and bdchwexit() -> bdcmemfree() manually before returning: bdcudcexit() tears down individual endpoint objects via bdcfreeep(), while bdchwexit() -> bdcmemfree() frees and NULLs the DMA-coherent status-report ring (bdc->srr.srbds) and kfree()s bdc->bdceparray. Both happen while the IRQ handler (bdcudcinterrupt, requested with IRQFSHARED) remains deliverable in the window up to the post-remove devm freeirq(). On receipt of a shared interrupt in that window, bdcudcinterrupt() dereferences bdc->srr.srbds[bdc->srr.dqpindex] (NULL or freed DMA) and dispatches srhandler callbacks that index into bdceparray, causing a NULL-deref or use-after-free. The same window affects the delayedwork bdc->funcwakenotify, which is armed from the IRQ handler via bdcsruspc() -> handlelinkstatechange() -> scheduledelayedwork() and may self-rearm from its own callback bdcfuncwaketimer(). No cancel exists anywhere in the driver, so a queued work item that fires after bdcremove() returns and the bdc structure is devm-freed dereferences freed memory. Replace devmrequestirq() with requestirq() and add an explicit freeirq(bdc->irq, bdc) in bdcremove(). Clear BDCGIE before freeirq() to stop the device from asserting interrupts, then freeirq() drains any in-flight handler, then canceldelayedworksync() drains the funcwakenotify delayed work. This ordering ensures the IRQ handler and delayed work cannot interfere with the subsequent endpoint and DMA teardown in bdcudcexit() and bdchwexit(). Wire the matching freeirq() into the bdcudcinit() error path so the IRQ is released on probe failure, and route the bdcinitep() failure through err0 instead of returning directly. This issue was found by an in-house static analysis tool.
Affected Software
Remediation
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In the Broadcom BDC UDC driver, clear BDC_GIE before teardown, replace devm_request_irq() with request_irq(), explicitly call free_irq(bdc->irq, bdc) in bdc_remove() before endpoint/DMA teardown, then call cancel_delayed_work_sync(&bdc->func_wake_notify) to drain delayed work. Wire the matching free_irq() into the bdc_udc_init() probe-failure path, and route bdc_init_ep() failure through err0 rather than returning directly.
Event History
Frequently Asked Questions
Which systems are realistically exposed to this issue?
Systems running an affected Ubuntu Linux kernel and using the Broadcom BDC USB Device Controller driver are exposed. The affected package list includes standard Ubuntu Linux kernels and AWS, Azure, GCP, FIPS, AWS FIPS, Azure FIPS, and GCP FIPS kernel variants.
What conditions are required to trigger the vulnerability?
An attacker needs local access and low privileges. Exploitation depends on a shared interrupt being delivered while the BDC driver is being removed and after its endpoint and DMA status-report resources have begun teardown.
Is this a remote network attack against a default host configuration?
The supplied vector identifies the attack vector as local and requires low privileges, with no user interaction. The data does not establish that the Broadcom BDC driver is enabled or in use by default on affected systems.
What happens if the race is triggered?
The IRQ handler can dereference a NULL or freed DMA status-report ring, or access a freed endpoint array. This can produce a NULL-pointer dereference or use-after-free, with impacts to confidentiality, integrity, and availability according to the supplied severity vector.