CVE-2026-43211: PCI: Fix pci_slot_trylock() error handling

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-06 · updated 2026-10-19
Weakness: CWE-667

Description

In the Linux kernel, the following vulnerability has been resolved: PCI: Fix pci_slot_trylock() error handling Commit a4e772898f8b ("PCI: Add missing bridge lock to pci_bus_lock()") delegates the bridge device's pci_dev_trylock() to pci_bus_trylock() in pci_slot_trylock(), but it forgets to remove the corresponding pci_dev_unlock() when pci_bus_trylock() fails. Before a4e772898f8b, the code did: if (!pci_dev_trylock(dev)) /* <- lock bridge device */ goto unlock; if (dev->subordinate) { if (!pci_bus_trylock(dev->subordinate)) { pci_dev_unlock(dev); /* <- unlock bridge device */ goto unlock; } } After a4e772898f8b the bridge-device lock is no longer taken, but the pci_dev_unlock(dev) on the failure path was left in place, leading to the bug. This yields one of two errors: 1. A warning that the lock is being unlocked when no one holds it. 2. An incorrect unlock of a lock that belongs to another thread. Fix it by removing the now-redundant pci_dev_unlock(dev) on the failure path. [Same patch later posted by Keith at https://patch.msgid.link/20260116184150.3013258-1-kbusch@meta.com]

Affected products

Linux kernel: from 4.19.322 before 4.20; from 5.4.284 before 5.5; from 5.10.226 before 5.10.252; from 5.15.167 before 5.15.202; from 6.1.110 before 6.1.165; from 6.6.51 before 6.6.128 — fixed in 4.20, 5.10.252, 5.15.202, 5.5, 6.1.165, 6.12.75

How to fix

Upgrade to a fixed version: Linux kernel 4.20, 5.10.252, 5.15.202, 5.5. Check the vendor advisory for mitigations.

References

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