CVE-2024-31076: In the Linux kernel, the following vulnerability has been resolved: genirq/cpuhotplug, x86/vector: Prevent vector leak during CPU offline The absenc...

Description

In the Linux kernel, the following vulnerability has been resolved: genirq/cpuhotplug, x86/vector: Prevent vector leak during CPU offline The absence of IRQD_MOVE_PCNTXT prevents immediate effectiveness of interrupt affinity reconfiguration via procfs. Instead, the change is deferred until the next instance of the interrupt being triggered on the original CPU. When the interrupt next triggers on the original CPU, the new affinity is enforced within __irq_move_irq(). A vector is allocated from the new CPU, but the old vector on the original CPU remains and is not immediately reclaimed. Instead, apicd->move_in_progress is flagged, and the reclaiming process is delayed until the next trigger of the interrupt on the new CPU. Upon the subsequent triggering of the interrupt on the new CPU, irq_complete_move() adds a task to the old CPU's vector_cleanup list if it remains online. Subsequently, the timer on the old CPU iterates over its vector_cleanup list, reclaiming old vectors. However, a rare scenario arises if the old CPU is outgoing before the interrupt triggers again on the new CPU. In that case irq_force_complete_move() is not invoked on the outgoing CPU to reclaim the old apicd->prev_vector because the interrupt isn't currently affine to the outgoing CPU, and irq_needs_fixup() returns false. Even though __vector_schedule_cleanup() is later called on the new CPU, it doesn't reclaim apicd->prev_vector; instead, it simply resets both apicd->move_in_progress and apicd->prev_vector to 0. As a result, the vector remains unreclaimed in vector_matrix, leading to a CPU vector leak. To address this issue, move the invocation of irq_force_complete_move() before the irq_needs_fixup() call to reclaim apicd->prev_vector, if the interrupt is currently or used to be affine to the outgoing CPU. Additionally, reclaim the vector in __vector_schedule_cleanup() as well, following a warning message, although theoretically it should never see apicd->move_in_progress with apicd->prev_cpu pointing to an offline CPU.

Metrics

CVSS 3.1

5.5/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.26%

17.1th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Linux	Linux Kernel	>= 4.13, < 4.19.316
Linux	Linux Kernel	>= 4.20, < 5.4.278
Linux	Linux Kernel	>= 5.5, < 5.10.219
Linux	Linux Kernel	>= 5.11, < 5.15.161
Linux	Linux Kernel	>= 5.16, < 6.1.93
Linux	Linux Kernel	>= 6.2, < 6.6.33
Linux	Linux Kernel	>= 6.7, < 6.9.4

References

Timeline

Published: Jun 21, 2024
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2024-31076?

In the Linux kernel, the following vulnerability has been resolved: genirq/cpuhotplug, x86/vector: Prevent vector leak during CPU offline The absence of IRQD_MOVE_PCNTXT prevents immediate effectiveness of interrupt affinity reconfiguration via procfs. Instead, the change is deferred until the next instance of the interrupt being triggered on the original CPU. When the interrupt next triggers on the original CPU, the new affinity is enforced within __irq_move_irq(). A vector is allocated from the new CPU, but the old vector on the original CPU remains and is not immediately reclaimed. Instead, apicd->move_in_progress is flagged, and the reclaiming process is delayed until the next trigger of the interrupt on the new CPU. Upon the subsequent triggering of the interrupt on the new CPU, irq_complete_move() adds a task to the old CPU's vector_cleanup list if it remains online. Subsequently, the timer on the old CPU iterates over its vector_cleanup list, reclaiming old vectors. However, a rare scenario arises if the old CPU is outgoing before the interrupt triggers again on the new CPU. In that case irq_force_complete_move() is not invoked on the outgoing CPU to reclaim the old apicd->prev_vector because the interrupt isn't currently affine to the outgoing CPU, and irq_needs_fixup() returns false. Even though __vector_schedule_cleanup() is later called on the new CPU, it doesn't reclaim apicd->prev_vector; instead, it simply resets both apicd->move_in_progress and apicd->prev_vector to 0. As a result, the vector remains unreclaimed in vector_matrix, leading to a CPU vector leak. To address this issue, move the invocation of irq_force_complete_move() before the irq_needs_fixup() call to reclaim apicd->prev_vector, if the interrupt is currently or used to be affine to the outgoing CPU. Additionally, reclaim the vector in __vector_schedule_cleanup() as well, following a warning message, although theoretically it should never see apicd->move_in_progress with apicd->prev_cpu pointing to an offline CPU.

How severe is CVE-2024-31076?

CVE-2024-31076 has a CVSS score of 5.5/10 (MEDIUM severity). The EPSS model estimates a 0.26% probability of exploitation in the next 30 days.

How do I fix CVE-2024-31076?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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