CVE-2024-56760

What it actually does

Incorrect legacy fallback assumption in pci_msi_domain_supports() and MSI enable path emits bogus warnings and mishandles platforms lacking irqdomain or legacy support.

Why it matters to the business

Boot-time warnings or PCI device initialization failures on RISC-V and LoongArch systems may reduce stability and complicate diagnostics in embedded or server deployments.

How an attack unfolds

An attacker with local access triggers pci_alloc_irq_vectors_affinity during device setup on an affected architecture; the flawed legacy check path produces warnings but does not grant code execution or privilege escalation.

How to fix it

Update to a kernel containing the corrected pci_msi_domain_supports() logic; no user-space changes required.

How to confirm the fix worked

Boot on RISC-V or LoongArch hardware, enable PCI devices, and confirm absence of the pci_msi_setup_msi_irqs warning in dmesg.

Typical attack path

1. Identify system lacking PCI/MSI irqdomain support
2. Load or initialize a PCI device requiring MSI/MSI-X
3. Invoke pci_msi_setup_msi_irqs via pci_alloc_irq_vectors_affinity
4. Trigger legacy fallback stub producing kernel warning

How to detect it

Search kernel logs for the warning emitted from pci_msi_setup_msi_irqs and inspect dmesg or journalctl around PCI device enumeration events.

What your security team should do

• Prioritize kernel upgrade on RISC-V and LoongArch systems within standard maintenance windows
• Monitor kernel logs for the specific warning string during PCI initialization
• Verify fixed kernel version in package manager before deployment