CVE-2023-53123: PCI: s390: Fix use-after-free of PCI resources with per-function hotplug
First published: Fri May 02 2025(Updated: )
In the Linux kernel, the following vulnerability has been resolved: PCI: s390: Fix use-after-free of PCI resources with per-function hotplug On s390 PCI functions may be hotplugged individually even when they belong to a multi-function device. In particular on an SR-IOV device VFs may be removed and later re-added. In commit a50297cf8235 ("s390/pci: separate zbus creation from scanning") it was missed however that struct pci_bus and struct zpci_bus's resource list retained a reference to the PCI functions MMIO resources even though those resources are released and freed on hot-unplug. These stale resources may subsequently be claimed when the PCI function re-appears resulting in use-after-free. One idea of fixing this use-after-free in s390 specific code that was investigated was to simply keep resources around from the moment a PCI function first appeared until the whole virtual PCI bus created for a multi-function device disappears. The problem with this however is that due to the requirement of artificial MMIO addreesses (address cookies) extra logic is then needed to keep the address cookies compatible on re-plug. At the same time the MMIO resources semantically belong to the PCI function so tying their lifecycle to the function seems more logical. Instead a simpler approach is to remove the resources of an individually hot-unplugged PCI function from the PCI bus's resource list while keeping the resources of other PCI functions on the PCI bus untouched. This is done by introducing pci_bus_remove_resource() to remove an individual resource. Similarly the resource also needs to be removed from the struct zpci_bus's resource list. It turns out however, that there is really no need to add the MMIO resources to the struct zpci_bus's resource list at all and instead we can simply use the zpci_bar_struct's resource pointer directly.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel |
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Reference Links
Frequently Asked Questions
What is the severity of CVE-2023-53123?
CVE-2023-53123 is classified as a medium severity vulnerability affecting the Linux kernel.
How do I fix CVE-2023-53123?
To fix CVE-2023-53123, update your Linux kernel to the latest version that contains the patch for this vulnerability.
What systems are affected by CVE-2023-53123?
CVE-2023-53123 affects systems running the Linux kernel, specifically those using s390 PCI functions and SR-IOV devices.
What does CVE-2023-53123 exploit?
CVE-2023-53123 exploits a use-after-free vulnerability in PCI resource management when dealing with per-function hotplug on s390.
Is there a workaround for CVE-2023-53123?
There may not be a feasible workaround for CVE-2023-53123, so applying the kernel patch is strongly recommended.
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