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CVE-2021-47061: KVM: Destroy I/O bus devices on unregister failure _after_ sync'ing SRCU

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2024-02-29 · updated 2026-08-04
• Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: Destroy I/O bus devices on unregister failure _after_ sync'ing SRCU If allocating a new instance of an I/O bus fails when unregistering a device, wait to destroy the device until after all readers are guaranteed to see the new null bus. Destroying devices before the bus is nullified could lead to use-after-free since readers expect the devices on their reference of the bus to remain valid.

Affected products

• Linux kernel: from 5.9 before 5.10.37; from 5.11 before 5.11.21; from 5.12 before 5.12.4 — fixed in 5.10.37, 5.11.21, 5.12.4

How to fix

Upgrade to a fixed version: Linux kernel 5.10.37, 5.11.21, 5.12.4. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/03c6cccedd3913006744faa252a4da5145299343
• https://git.kernel.org/stable/c/2ee3757424be7c1cd1d0bbfa6db29a7edd82a250
• https://git.kernel.org/stable/c/30f46c6993731efb2a690c9197c0fd9ed425da2d
• https://git.kernel.org/stable/c/4e899ca848636b37e9ac124bc1723862a7d7d927
• https://git.kernel.org/stable/c/03c6cccedd3913006744faa252a4da5145299343
• https://git.kernel.org/stable/c/2ee3757424be7c1cd1d0bbfa6db29a7edd82a250
• https://git.kernel.org/stable/c/30f46c6993731efb2a690c9197c0fd9ed425da2d
• https://git.kernel.org/stable/c/4e899ca848636b37e9ac124bc1723862a7d7d927

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