CVE-2025-39958 iommu/s390: Make attach succeed when the device was surprise removed
A flaw in the Linux kernel's s390 IOMMU driver causes a kernel warning and potential instability when attaching a surprise-removed PCI device.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39958?
CVE-2025-39958 is a high-severity denial of service vulnerability in Linux kernel, published on 9 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
iommu/s390: Make attach succeed when the device was surprise removed
When a PCI device is removed with surprise hotplug, there may still be attempts to attach the device to the default domain as part of tear down via (__iommu_release_dma_ownership()), or because the removal happens during probe (__iommu_probe_device()). In both cases zpci_register_ioat() fails with a cc value indicating that the device handle is invalid. This is because the device is no longer part of the instance as far as the hypervisor is concerned.
Currently this leads to an error return and s390_iommu_attach_device() fails. This triggers the WARN_ON() in __iommu_group_set_domain_nofail() because attaching to the default domain must never fail.
With the device fenced by the hypervisor no DMAs to or from memory are possible and the IOMMU translations have no effect. Proceed as if the registration was successful and let the hotplug event handling clean up the device.
This is similar to how devices in the error state are handled since commit 59bbf596791b ("iommu/s390: Make attach succeed even if the device is in error state") except that for removal the domain will not be registered later. This approach was also previously discussed at the link.
Handle both cases, error state and removal, in a helper which checks if the error needs to be propagated or ignored. Avoid magic number condition codes by using the pre-existing, but never used, defines for PCI load/store condition codes and rename them to reflect that they apply to all PCI instructions.
Which versions are affected by CVE-2025-39958?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39958?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-39958 being exploited?
There is no known exploitation of CVE-2025-39958 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-39958, DEBIAN-CVE-2025-39958, GHSA-p5vh-p63c-cg4v, ROOT-OS-DEBIAN-13-CVE-2025-39958, ROOT-OS-UBUNTU-2204-CVE-2025-39958, ROOT-OS-UBUNTU-2404-CVE-2025-39958 and 1 more.