PT-2020-17193 · Xen · Xen
Roger Pau Monné
·
Published
2020-12-15
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Updated
2024-06-15
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CVE-2020-29567
CVSS v3.1
6.2
Medium
| Vector | AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Name of the Vulnerable Software and Affected Versions
Xen versions 4.14.x
Description
An issue was discovered in Xen when moving IRQs between CPUs to distribute the load of IRQ handling. IRQ vectors are dynamically allocated and de-allocated on the relevant CPUs. De-allocation has to happen when certain constraints are met. If these conditions are not met when first checked, the checking CPU may send an interrupt to itself, in the expectation that this IRQ will be delivered only after the condition preventing the cleanup has cleared. For two specific IRQ vectors, this expectation was violated, resulting in a continuous stream of self-interrupts, which renders the CPU effectively unusable. A domain with a passed through PCI device can cause lockup of a physical CPU, resulting in a Denial of Service (DoS) to the entire host. Only x86 systems are vulnerable, while Arm systems are not. The issue can be exploited by guests with physical PCI devices passed through to them.
Recommendations
For Xen version 4.14.x, to resolve the issue, ensure that guests do not have physical PCI devices passed through to them, or restrict the ability of guests to cause a lockup of a physical CPU. As a temporary workaround, consider disabling the passing through of physical PCI devices to guests until a patch is available.
Fix
Allocation of Resources Without Limits
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Weakness Enumeration
Related Identifiers
Affected Products
Xen