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

usb: gadget: f_midi: cancel pending IN work before freeing the midi object

The f_midi driver embeds a work item (midi->work) whose handler,
f_midi_in_work(), dereferences the enclosing struct f_midi through
container_of(). This work is armed from two sites: f_midi_complete(),
on a normal IN-endpoint completion, and f_midi_in_trigger(), on an ALSA
rawmidi output-stream start.

Neither f_midi_disable() nor f_midi_unbind() cancels midi->work.
f_midi_disable() only disables the endpoints and drains the in_req_fifo;
it does not synchronize the work item, and the sound card is released
asynchronously to the final free of the midi object.

The midi object is reference-counted (midi->free_ref) and is freed in
f_midi_free() only once both the usb_function reference and the rawmidi
private_data reference have been dropped. In f_midi_unbind(),
f_midi_disable() runs before the sound card is released, so while the
USB endpoints are already disabled the rawmidi device is still usable by
an open substream. A concurrent userspace write on such a substream can
reach f_midi_in_trigger() and queue midi->work again after
f_midi_disable() has returned. A work item armed this way may still be
pending when the last reference drops and f_midi_free() proceeds to
kfree(midi), letting f_midi_in_work() dereference the struct after it
has been freed, a use-after-free.

For this reason cancelling midi->work in f_midi_disable() would not be
sufficient: the ALSA trigger path can rearm the work after disable()
returns. Cancelling at the refcount-zero free site is the boundary
after which neither arming source can survive, because by then both
references that keep the midi object alive have been dropped: the USB
endpoints are already disabled and the rawmidi device has been released.

Fix this by calling cancel_work_sync(&midi->work) in the refcount-zero
block of f_midi_free(), before the embedded work_struct is freed along
with the rest of the structure. opts->lock is a sleeping mutex, so
calling cancel_work_sync() under it is permitted, and the handler takes
midi->transmit_lock rather than opts->lock, so no self-deadlock can
occur while it waits for a running instance of the work to finish.

This issue was found by an in-house static analysis tool.
Published: 2026-08-06
Score: n/a
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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History

Thu, 06 Aug 2026 07:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_midi: cancel pending IN work before freeing the midi object The f_midi driver embeds a work item (midi->work) whose handler, f_midi_in_work(), dereferences the enclosing struct f_midi through container_of(). This work is armed from two sites: f_midi_complete(), on a normal IN-endpoint completion, and f_midi_in_trigger(), on an ALSA rawmidi output-stream start. Neither f_midi_disable() nor f_midi_unbind() cancels midi->work. f_midi_disable() only disables the endpoints and drains the in_req_fifo; it does not synchronize the work item, and the sound card is released asynchronously to the final free of the midi object. The midi object is reference-counted (midi->free_ref) and is freed in f_midi_free() only once both the usb_function reference and the rawmidi private_data reference have been dropped. In f_midi_unbind(), f_midi_disable() runs before the sound card is released, so while the USB endpoints are already disabled the rawmidi device is still usable by an open substream. A concurrent userspace write on such a substream can reach f_midi_in_trigger() and queue midi->work again after f_midi_disable() has returned. A work item armed this way may still be pending when the last reference drops and f_midi_free() proceeds to kfree(midi), letting f_midi_in_work() dereference the struct after it has been freed, a use-after-free. For this reason cancelling midi->work in f_midi_disable() would not be sufficient: the ALSA trigger path can rearm the work after disable() returns. Cancelling at the refcount-zero free site is the boundary after which neither arming source can survive, because by then both references that keep the midi object alive have been dropped: the USB endpoints are already disabled and the rawmidi device has been released. Fix this by calling cancel_work_sync(&midi->work) in the refcount-zero block of f_midi_free(), before the embedded work_struct is freed along with the rest of the structure. opts->lock is a sleeping mutex, so calling cancel_work_sync() under it is permitted, and the handler takes midi->transmit_lock rather than opts->lock, so no self-deadlock can occur while it waits for a running instance of the work to finish. This issue was found by an in-house static analysis tool.
Title usb: gadget: f_midi: cancel pending IN work before freeing the midi object
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-06T07:06:25.953Z

Reserved: 2026-07-19T15:36:31.798Z

Link: CVE-2026-64584

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-06T09:00:10Z

Weaknesses

No weakness.