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

Vulnerability summary

CVE-2021-47061 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 15.5% of scored vulnerabilities.

Timeline

1. 29-02-2024
   PublishedVulnerability first disclosed.
2. 05-08-2026
   Last modifiedVulnerability information updated.

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.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.