PCI: Protect pci_driver->sriov_configure() usage with device_lock()

Every method in struct device_driver or structures derived from it like
struct pci_driver MUST provide exclusion vs the driver's ->remove() method,
usually by using device_lock().

Protect use of pci_driver->sriov_configure() by holding the device lock
while calling it.

The PCI core sets the pci_dev->driver pointer in local_pci_probe() before
calling ->probe() and only clears it after ->remove().  This means driver's
->sriov_configure() callback will happily race with probe() and remove(),
most likely leading to BUGs, since drivers don't expect this.

Remove the iov lock completely, since we remove the last user.

[bhelgaas: changelog, thanks to Christoph for locking rule]
Link: http://lkml.kernel.org/r/20170522225023.14010-1-jakub.kicinski@netronome.com
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 31e9961..7755559 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -472,7 +472,6 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 				  const char *buf, size_t count)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	struct pci_sriov *iov = pdev->sriov;
 	int ret;
 	u16 num_vfs;
 
@@ -483,7 +482,7 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 	if (num_vfs > pci_sriov_get_totalvfs(pdev))
 		return -ERANGE;
 
-	mutex_lock(&iov->dev->sriov->lock);
+	device_lock(&pdev->dev);
 
 	if (num_vfs == pdev->sriov->num_VFs)
 		goto exit;
@@ -518,7 +517,7 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 			 num_vfs, ret);
 
 exit:
-	mutex_unlock(&iov->dev->sriov->lock);
+	device_unlock(&pdev->dev);
 
 	if (ret < 0)
 		return ret;