CVE-2023-54081: xen: speed up grant-table reclaim

Severity: unknown
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: 2025-12-24 · updated 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: xen: speed up grant-table reclaim When a grant entry is still in use by the remote domain, Linux must put it on a deferred list. Normally, this list is very short, because the PV network and block protocols expect the backend to unmap the grant first. However, Qubes OS's GUI protocol is subject to the constraints of the X Window System, and as such winds up with the frontend unmapping the window first. As a result, the list can grow very large, resulting in a massive memory leak and eventual VM freeze. To partially solve this problem, make the number of entries that the VM will attempt to free at each iteration tunable. The default is still 10, but it can be overridden via a module parameter. This is Cc: stable because (when combined with appropriate userspace changes) it fixes a severe performance and stability problem for Qubes OS users.

Affected products

Linux kernel: 3.5 — fixed in 6.5

How to fix

Upgrade to a fixed version: Linux kernel 6.5. Check the vendor advisory for mitigations.

References

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