CVE-2024-46750

In the Linux kernel, the following vulnerability has been resolved:

PCI: Add missing bridge lock to pci_bus_lock()

One of the true positives that the cfg_access_lock lockdep effort identified is this sequence:

WARNING: CPU: 14 PID: 1 at drivers/pci/pci.c:4886 pci_bridge_secondary_bus_reset+0x5d/0x70 RIP: 0010:pci_bridge_secondary_bus_reset+0x5d/0x70 Call Trace: ? __warn+0x8c/0x190 ? pci_bridge_secondary_bus_reset+0x5d/0x70 ? report_bug+0x1f8/0x200 ? handle_bug+0x3c/0x70 ? exc_invalid_op+0x18/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? pci_bridge_secondary_bus_reset+0x5d/0x70 pci_reset_bus+0x1d8/0x270 vmd_probe+0x778/0xa10 pci_device_probe+0x95/0x120

Where pci_reset_bus() users are triggering unlocked secondary bus resets. Ironically pci_bus_reset(), several calls down from pci_reset_bus(), uses pci_bus_lock() before issuing the reset which locks everything but the bridge itself.

For the same motivation as adding:

bridge = pci_upstream_bridge(dev); if (bridge) pci_dev_lock(bridge);

to pci_reset_function() for the bus and cxl_bus reset cases, add pci_dev_lock() for @bus->self to pci_bus_lock().

[bhelgaas: squash in recursive locking deadlock fix from Keith Busch: https://lore.kernel.org/r/20240711193650.701834-1-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/04e85a3285b0e5c5af6fd2c0fd6e95ffecc01945
• https://git.kernel.org/stable/c/0790b89c7e911003b8c50ae50e3ac7645de1fae9
• https://git.kernel.org/stable/c/7253b4fed46471cc247c6cacefac890a8472c083
• https://git.kernel.org/stable/c/78c6e39fef5c428960aff742149bba302dd46f5a
• https://git.kernel.org/stable/c/81c68e218ab883dfa368460a59b674084c0240da
• https://git.kernel.org/stable/c/a4e772898f8bf2e7e1cf661a12c60a5612c4afab
• https://git.kernel.org/stable/c/df77a678c33871a6e4ac5b54a71662f1d702335b
• https://git.kernel.org/stable/c/e2355d513b89a2cb511b4ded0deb426cdb01acd0