CVE-2026-43211

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 devices 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]

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/0425aaf20b407d2f2cf3bf469808e4a35f9abb8b
• https://git.kernel.org/stable/c/8b08ea9690b212b7bf7f12414039259cf34b1aa0
• https://git.kernel.org/stable/c/9368d1ee62829b08aa31836b3ca003803caf0b72
• https://git.kernel.org/stable/c/943ed56606a7ab2fe5a99cad572dd17d484310c7
• https://git.kernel.org/stable/c/a19b61fdb958ffadbba85b43c991eb9fc70c1c1c
• https://git.kernel.org/stable/c/bd435f4b738130d732ef64e0e57e45185f77165d
• https://git.kernel.org/stable/c/ebb27b7399ab8b9eb1f792b329aa5f6250c590d4
• https://git.kernel.org/stable/c/fbe06a3058114bf95a17a4941b205f4b321c6f0a