CVE-2025-37843 PCI: pciehp: Avoid unnecessary device replacement check
A race condition in the Linux kernel PCI hotplug driver can cause a deadlock during device removal, leading to system denial of service.
- 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-2025-37843?
CVE-2025-37843 is a medium-severity vulnerability in Linux kernel, published on 9 May 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:
PCI: pciehp: Avoid unnecessary device replacement check
Hot-removal of nested PCI hotplug ports suffers from a long-standing race condition which can lead to a deadlock: A parent hotplug port acquires pci_lock_rescan_remove(), then waits for pciehp to unbind from a child hotplug port. Meanwhile that child hotplug port tries to acquire pci_lock_rescan_remove() as well in order to remove its own children.
The deadlock only occurs if the parent acquires pci_lock_rescan_remove() first, not if the child happens to acquire it first.
Several workarounds to avoid the issue have been proposed and discarded over the years, e.g.:
https://lore.kernel.org/r/4c882e25194ba8282b78fe963fec8faae7cf23eb.1529173804.git.lukas@wunner.de/
A proper fix is being worked on, but needs more time as it is nontrivial and necessarily intrusive.
Recent commit 9d573d19547b ("PCI: pciehp: Detect device replacement during system sleep") provokes more frequent occurrence of the deadlock when removing more than one Thunderbolt device during system sleep. The commit sought to detect device replacement, but also triggered on device removal. Differentiating reliably between replacement and removal is impossible because pci_get_dsn() returns 0 both if the device was removed, as well as if it was replaced with one lacking a Device Serial Number.
Avoid the more frequent occurrence of the deadlock by checking whether the hotplug port itself was hot-removed. If so, there's no sense in checking whether its child device was replaced.
This works because the ->resume_noirq() callback is invoked in top-down order for the entire hierarchy: A parent hotplug port detecting device replacement (or removal) marks all children as removed using pci_dev_set_disconnected() and a child hotplug port can then reliably detect being removed.
Weakness: CWE-667
Which versions are affected by CVE-2025-37843?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-37843?
Apply the vendor's patch.
Is CVE-2025-37843 being exploited?
There is no known exploitation of CVE-2025-37843 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-37843, DEBIAN-CVE-2025-37843, GHSA-rjpx-6frc-3vgp, UBUNTU-CVE-2025-37843.