Bug 2422794 (CVE-2025-68312)

Summary: CVE-2025-68312 kernel: usbnet: Prevents free active kevent
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A use-after-free vulnerability was found in the Linux kernel's usbnet driver. When a usbnet device is unregistered before a scheduled kevent work item executes, free_netdev() frees memory that the pending kevent will later access. This occurs because kevent cancellation is missing before device cleanup when the device was never brought up.
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Description OSIDB Bzimport 2025-12-16 16:01:54 UTC 
In the Linux kernel, the following vulnerability has been resolved:

usbnet: Prevents free active kevent

The root cause of this issue are:
1. When probing the usbnet device, executing usbnet_link_change(dev, 0, 0);
put the kevent work in global workqueue. However, the kevent has not yet
been scheduled when the usbnet device is unregistered. Therefore, executing
free_netdev() results in the "free active object (kevent)" error reported
here.

2. Another factor is that when calling usbnet_disconnect()->unregister_netdev(),
if the usbnet device is up, ndo_stop() is executed to cancel the kevent.
However, because the device is not up, ndo_stop() is not executed.

The solution to this problem is to cancel the kevent before executing
free_netdev().
Comment 1 Alexander B 2025-12-16 20:01:19 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025121654-CVE-2025-68312-63bb@gregkh/T