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

PCI: Avoid pci_dev_lock() AB/BA deadlock with sriov_numvfs_store()

The sysfs sriov_numvfs_store() path acquires the device lock before the
config space access lock:

  sriov_numvfs_store
    device_lock                 # A (1) acquire device lock
    sriov_configure
      vfio_pci_sriov_configure  # (for example)
        vfio_pci_core_sriov_configure
          pci_disable_sriov
            sriov_disable
              pci_cfg_access_lock
                pci_wait_cfg    # B (4) wait for dev->block_cfg_access == 0

Previously, pci_dev_lock() acquired the config space access lock before the
device lock:

  pci_dev_lock
    pci_cfg_access_lock
      dev->block_cfg_access = 1 # B (2) set dev->block_cfg_access = 1
    device_lock                 # A (3) wait for device lock

Any path that uses pci_dev_lock(), e.g., pci_reset_function(), may
deadlock with sriov_numvfs_store() if the operations occur in the sequence
(1) (2) (3) (4).

Avoid the deadlock by reversing the order in pci_dev_lock() so it acquires
the device lock before the config space access lock, the same as the
sriov_numvfs_store() path.

[bhelgaas: combined and adapted commit log from Jay Zhou's independent
subsequent posting:
https://lore.kernel.org/r/[email protected]]

https://git.kernel.org/stable/c/2cdd5284035322795b0964f899eefba254cfe483

https://git.kernel.org/stable/c/59ea6b3ae51df7cd6bfd84c9c0030609b9315622

https://git.kernel.org/stable/c/a91ee0e9fca9d7501286cfbced9b30a33e52740a

https://git.kernel.org/stable/c/aed6d4d519210c28817948f34c53b6e058e0456c

https://git.kernel.org/stable/c/c3c6dc1853b8bf3c718f96fd8480a6eb09ba4831

https://git.kernel.org/stable/c/c9a81f9ed6ae3554621d6a50220b1bc74b67d81e

https://git.kernel.org/stable/c/da9792920ab525b8a932aa9aeee34529ad7b83f7

https://git.kernel.org/stable/c/ea047f51172aa68841adef7f52d375002438b8f0

https://git.kernel.org/stable/c/eff3587b9c01439b738298475e555c028ac9f55e