Bug 2418841 (CVE-2025-40223)

Summary:	CVE-2025-40223 kernel: most: usb: Fix use-after-free in hdm_disconnect
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-12-04 16:03:45 UTC

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

most: usb: Fix use-after-free in hdm_disconnect

hdm_disconnect() calls most_deregister_interface(), which eventually
unregisters the MOST interface device with device_unregister(iface->dev).
If that drops the last reference, the device core may call release_mdev()
immediately while hdm_disconnect() is still executing.

The old code also freed several mdev-owned allocations in
hdm_disconnect() and then performed additional put_device() calls.
Depending on refcount order, this could lead to use-after-free or
double-free when release_mdev() ran (or when unregister paths also
performed puts).

Fix by moving the frees of mdev-owned allocations into release_mdev(),
so they happen exactly once when the device is truly released, and by
dropping the extra put_device() calls in hdm_disconnect() that are
redundant after device_unregister() and most_deregister_interface().

This addresses the KASAN slab-use-after-free reported by syzbot in
hdm_disconnect(). See report and stack traces in the bug link below.

Comment 1 Alexander B 2025-12-05 15:00:08 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025120458-CVE-2025-40223-66bd@gregkh/T