CVE-2024-31076

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxf0383c24b4855f6a4b5a358c7b2d2c16e0437e9b < a40209d355afe4ed6d533507838c9e5cd70a76d8affected
LinuxLinuxf0383c24b4855f6a4b5a358c7b2d2c16e0437e9b < f5f4675960609d8c5ee95f027fbf6ce380f98372affected
LinuxLinuxf0383c24b4855f6a4b5a358c7b2d2c16e0437e9b < 6752dfcfff3ac3e16625ebd3f0ad9630900e7e76affected
LinuxLinuxf0383c24b4855f6a4b5a358c7b2d2c16e0437e9b < 9eeda3e0071a329af1eba15f4e57dc39576bb420affected
LinuxLinuxf0383c24b4855f6a4b5a358c7b2d2c16e0437e9b < e9c96d01d520498b169ce734a8ad1142bef86a30affected
LinuxLinuxf0383c24b4855f6a4b5a358c7b2d2c16e0437e9b < 59f86a2908380d09cdc726461c0fbb8d8579c99faffected
LinuxLinuxf0383c24b4855f6a4b5a358c7b2d2c16e0437e9b < ebfb16fc057a016abb46a9720a54abf0d4f6abe1affected
LinuxLinuxf0383c24b4855f6a4b5a358c7b2d2c16e0437e9b < a6c11c0a5235fb144a65e0cb2ffd360ddc1f6c32affected
LinuxLinux4.13affected
LinuxLinux0 < 4.13unaffected
LinuxLinux4.19.316 <= 4.19.*unaffected
LinuxLinux5.4.278 <= 5.4.*unaffected
LinuxLinux5.10.219 <= 5.10.*unaffected
LinuxLinux5.15.161 <= 5.15.*unaffected
LinuxLinux6.1.93 <= 6.1.*unaffected
LinuxLinux6.6.33 <= 6.6.*unaffected
LinuxLinux6.9.4 <= 6.9.*unaffected
LinuxLinux6.10 <= *unaffected

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References