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

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[ Upstream commit a91ee0e9fc ]

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/20220404062539.1710-1-jianjay.zhou@huawei.com]
Link: https://lore.kernel.org/linux-pci/1583489997-17156-1-git-send-email-yangyicong@hisilicon.com/
Also-posted-by: Jay Zhou <jianjay.zhou@huawei.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Yicong Yang 2022-04-04 14:25:39 +08:00 committed by Greg Kroah-Hartman
parent 5f4367448f
commit ea047f5117
1 changed files with 5 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

10
drivers/pci/pci.c
View file

@ -5113,19 +5113,19 @@ static int pci_reset_bus_function(struct pci_dev *dev, bool probe)
void pci_dev_lock(struct pci_dev *dev)
{
pci_cfg_access_lock(dev);
/* block PM suspend, driver probe, etc. */
device_lock(&dev->dev);
pci_cfg_access_lock(dev);
}
EXPORT_SYMBOL_GPL(pci_dev_lock);
/* Return 1 on successful lock, 0 on contention */
int pci_dev_trylock(struct pci_dev *dev)
{
if (pci_cfg_access_trylock(dev)) {
if (device_trylock(&dev->dev))
if (device_trylock(&dev->dev)) {
if (pci_cfg_access_trylock(dev))
return 1;
pci_cfg_access_unlock(dev);
device_unlock(&dev->dev);
}
return 0;
@ -5134,8 +5134,8 @@ EXPORT_SYMBOL_GPL(pci_dev_trylock);
void pci_dev_unlock(struct pci_dev *dev)
{
device_unlock(&dev->dev);
pci_cfg_access_unlock(dev);
device_unlock(&dev->dev);
}
EXPORT_SYMBOL_GPL(pci_dev_unlock);