Vulnerability details

In the Linux kernel, the following vulnerability has been resolved: vfio/cdx: Serialize VFIO_DEVICE_SET_IRQS with a per-device mutex vfio_cdx_set_msi_trigger() reads vdev->config_msi and operates on the vdev->cdx_irqs array based on its value, but provides no serialization against concurrent VFIO_DEVICE_SET_IRQS ioctls. Two callers can race such that one observes config_msi as set while another clears it and frees cdx_irqs via vfio_cdx_msi_disable(), resulting in a use-after-free of the cdx_irqs array. Add a cdx_irqs_lock mutex to struct vfio_cdx_device and acquire it in vfio_cdx_set_msi_trigger(), which is the single chokepoint through which all updates to config_msi, cdx_irqs, and msi_count flow, covering both the ioctl path and the close-device cleanup path. This keeps the test of config_msi atomic with the subsequent enable, disable, or trigger operations. Drop the pre-call !cdx_irqs test from vfio_cdx_irqs_cleanup() as part of this change: the optimization it provided is redundant with the !config_msi early-return inside vfio_cdx_msi_disable(), and leaving the test in place would be an unsynchronized read of state the new lock is meant to protect.

• https://git.kernel.org/stable/c/ddf96e23c366c566283fce8377928851fa7f5e81
• https://git.kernel.org/stable/c/7b436ade16cc81095d79b79f8efa3af0a4f5c5a2
• https://git.kernel.org/stable/c/7530f34ec0ca1438d45a75dcb43183a1cc92eced
• https://git.kernel.org/stable/c/670e8864b1a218d72f08db40d0103adf38fa1d9b