CVE-2024-26810 - Resolving Linux Kernel Vulnerability: VFIO/PCI Locks External INTx Masking Operations

In recent times, a new vulnerability (CVE-2024-26810) has been discovered in the Linux kernel which affects the Virtual Function I/O (VFIO) PCI subsystem. This vulnerability revolves around INTx masking operations which could lead to potential race conditions and system instability. To address this issue, developers have introduced new wrappers that add necessary locking mechanisms to paths outside of the core interrupt code. This article will delve into the details of the vulnerability, the associated code snippet, original references, and exploit details.

Vulnerability Details

The vulnerability in question affects the VFIO/PCI subsystem of the Linux kernel, specifically the mask operations through config space changes to DisINTx. This vulnerability may lead to race conditions during INTx configuration changes via ioctl. To address this issue, wrappers have been introduced that provide the necessary locking mechanisms to mitigate this vulnerability.

The exploit manifests itself when DisINTx clearing from config space races changes of the interrupt configuration. The proper locking for paths outside of the core interrupt code ensures that the tested is_intx() function holds the igate lock. Consequently, this helps prevent potential race conditions and maintains system stability.

Code Snippet

To resolve this vulnerability, developers have introduced the following code snippet that adds the necessary locking for paths outside of the core interrupt code.

void vfio_pci_intx_mask(struct vfio_pci_device *vdev)
{
  unsigned long flags;

  spin_lock_irqsave(&vdev->igate, flags);
  if (is_intx(vdev))
      vfio_intx_mask(vdev->intx_info);
  spin_unlock_irqrestore(&vdev->igate, flags);
}

void vfio_pci_intx_unmask(struct vfio_pci_device *vdev)
{
  unsigned long flags;

  spin_lock_irqsave(&vdev->igate, flags);
  if (is_intx(vdev))
      vfio_intx_unmask(vdev->intx_info);
  spin_unlock_irqrestore(&vdev->igate, flags);
}

Original References

1. Linux Kernel Mailing List (LKML): To gain more insight into the issue, refer to the LKML article where the patch introducing the wrappers was initially posted - LKML Patch
2. The Linux Kernel Archives: The complete Linux kernel sources can be explored to understand the vulnerable code. The specific patch can be found in the Changelog - Linux Kernel Source

Exploit Details

The potential exploit would involve triggering race conditions during INTx configuration changes via ioctl. This could lead to system instability and other undesirable outcomes. However, the introduced changes (locking mechanisms and synchronization) effectively mitigate this vulnerability by preventing race conditions. Users are advised to update their kernel to the latest patched version, which includes this vulnerability fix.

Conclusion

In conclusion, by addressing the CVE-2024-26810 vulnerability in the VFIO/PCI subsystem of the Linux kernel, developers have eliminated potential race conditions that could lead to system instability. Users are strongly advised to update their kernel to the latest patched version in order to maintain optimal system performance and security.

Timeline

Published on: 04/05/2024 09:15:09 UTC
Last modified on: 06/25/2024 21:15:58 UTC