"value":"In the Linux kernel, the following vulnerability has been resolved:\n\nPCI: s390: Fix use-after-free of PCI resources with per-function hotplug\n\nOn s390 PCI functions may be hotplugged individually even when they\nbelong to a multi-function device. In particular on an SR-IOV device VFs\nmay be removed and later re-added.\n\nIn commit a50297cf8235 (\"s390/pci: separate zbus creation from\nscanning\") it was missed however that struct pci_bus and struct\nzpci_bus's resource list retained a reference to the PCI functions MMIO\nresources even though those resources are released and freed on\nhot-unplug. These stale resources may subsequently be claimed when the\nPCI function re-appears resulting in use-after-free.\n\nOne idea of fixing this use-after-free in s390 specific code that was\ninvestigated was to simply keep resources around from the moment a PCI\nfunction first appeared until the whole virtual PCI bus created for\na multi-function device disappears. The problem with this however is\nthat due to the requirement of artificial MMIO addreesses (address\ncookies) extra logic is then needed to keep the address cookies\ncompatible on re-plug. At the same time the MMIO resources semantically\nbelong to the PCI function so tying their lifecycle to the function\nseems more logical.\n\nInstead a simpler approach is to remove the resources of an individually\nhot-unplugged PCI function from the PCI bus's resource list while\nkeeping the resources of other PCI functions on the PCI bus untouched.\n\nThis is done by introducing pci_bus_remove_resource() to remove an\nindividual resource. Similarly the resource also needs to be removed\nfrom the struct zpci_bus's resource list. It turns out however, that\nthere is really no need to add the MMIO resources to the struct\nzpci_bus's resource list at all and instead we can simply use the\nzpci_bar_struct's resource pointer directly."
