In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Use device rbtree in iopf reporting path The existing I/O page fault handler currently locates the PCI device by calling pci_get_domain_bus_and_slot(). This function searches the list of all PCI devices until the desired device is found. To improve lookup efficiency, replace it with device_rbtree_find() to search the device within the probed device rbtree. The I/O page fault is initiated by the device, which does not have any synchronization mechanism with the software to ensure that the device stays in the probed device tree. Theoretically, a device could be released by the IOMMU subsystem after device_rbtree_find() and before iopf_get_dev_fault_param(), which would cause a use-after-free problem. Add a mutex to synchronize the I/O page fault reporting path and the IOMMU release device path. This lock doesn't introduce any performance overhead, as the conflict between I/O page fault reporting and device releasing is very rare.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.