CVE-2026-89795PCI: Allow per function PCI slots to fix slot reset on s390

Official description

In the Linux kernel, the following vulnerability has been resolved: PCI: Allow per function PCI slots to fix slot reset on s390 On s390 systems, which use a machine level hypervisor, PCI devices are always accessed through a form of PCI pass-through which fundamentally operates on a per PCI function granularity. This is also reflected in the s390 PCI hotplug driver which creates hotplug slots for individual PCI functions. Its reset_slot() function, which is a wrapper for zpci_hot_reset_device(), thus also resets individual functions. Currently, the pci_create_slot() assigns the same pci_slot object to multifunction devices. This approach worked fine on s390 systems that only exposed virtual functions as individual PCI domains to the operating system. Since commit 44510d6fa0c0 ("s390/pci: Handling multifunctions") s390 supports exposing the topology of multifunction PCI devices by grouping them in a shared PCI domain. This creates a problem when resetting a function through the hotplug driver's slot_reset() interface. When attempting to reset a function through the hotplug driver, the shared slot assignment causes the wrong function to be reset instead of the intended one. It also leaks memory as we do create a pci_slot object for the function, but don't correctly free it in pci_slot_release(). Add a flag for struct pci_slot to allow per function PCI slots for functions managed through a hypervisor, which exposes individual PCI functions while retaining the topology. Since we can use all 8 bits for slot 'number' (for ARI devices), change slot 'number' u16 to account for special values PCI_SLOT_PLACEHOLDER and PCI_SLOT_ALL_DEVICES.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/afdd497ca3836eda13530ab75b416d52f6d6129a
• https://git.kernel.org/stable/c/b4a80e9e639cf09ef5c66b7f262c9cb5ab37bdde
• https://git.kernel.org/stable/c/0d1a7d67f45645106578d65181e4e492dd20ed79
• https://git.kernel.org/stable/c/2050d900f9adbd6d6f38d30e182bcd9ad3108467
• https://git.kernel.org/stable/c/ecdcceed4d377b02d4ea036b65f83f962c38ede7
• https://git.kernel.org/stable/c/dcc5bec09e23bbc4f9de055a11fce9937244f2c8