Revert "PCI: Use to_pci_driver() instead of pci_dev->driver"

This reverts commit 2a4d9408c9e8b6f6fc150c66f3fef755c9e20d4a.

Robert reported a NULL pointer dereference caused by the PCI core
(local_pci_probe()) calling the i2c_designware_pci driver's
.runtime_resume() method before the .probe() method.  i2c_dw_pci_resume()
depends on initialization done by i2c_dw_pci_probe().

Prior to 2a4d9408c9e8 ("PCI: Use to_pci_driver() instead of
pci_dev->driver"), pci_pm_runtime_resume() avoided calling the
.runtime_resume() method because pci_dev->driver had not been set yet.

2a4d9408c9e8 and b5f9c644eb1b ("PCI: Remove struct pci_dev->driver"),
removed pci_dev->driver, replacing it by device->driver, which *has* been
set by this time, so pci_pm_runtime_resume() called the .runtime_resume()
method when it previously had not.

Fixes: 2a4d9408c9e8 ("PCI: Use to_pci_driver() instead of pci_dev->driver")
Link: https://lore.kernel.org/linux-i2c/CAP145pgdrdiMAT7=-iB1DMgA7t_bMqTcJL4N0=6u8kNY3EU0dw@mail.gmail.com/
Reported-by: Robert Święcki <robert@swiecki.net>
Tested-by: Robert Święcki <robert@swiecki.net>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 9 insertions, 15 deletions

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 1d7a7c5b5307..0267977c9f17 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -164,15 +164,13 @@ static ssize_t sriov_vf_total_msix_show(struct device *dev,
 					char *buf)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	struct pci_driver *pdrv;
 	u32 vf_total_msix = 0;
 
 	device_lock(dev);
-	pdrv = to_pci_driver(dev->driver);
-	if (!pdrv || !pdrv->sriov_get_vf_total_msix)
+	if (!pdev->driver || !pdev->driver->sriov_get_vf_total_msix)
 		goto unlock;
 
-	vf_total_msix = pdrv->sriov_get_vf_total_msix(pdev);
+	vf_total_msix = pdev->driver->sriov_get_vf_total_msix(pdev);
 unlock:
 	device_unlock(dev);
 	return sysfs_emit(buf, "%u\n", vf_total_msix);
@@ -185,7 +183,6 @@ static ssize_t sriov_vf_msix_count_store(struct device *dev,
 {
 	struct pci_dev *vf_dev = to_pci_dev(dev);
 	struct pci_dev *pdev = pci_physfn(vf_dev);
-	struct pci_driver *pdrv;
 	int val, ret = 0;
 
 	if (kstrtoint(buf, 0, &val) < 0)
@@ -195,14 +192,13 @@ static ssize_t sriov_vf_msix_count_store(struct device *dev,
 		return -EINVAL;
 
 	device_lock(&pdev->dev);
-	pdrv = to_pci_driver(dev->driver);
-	if (!pdrv || !pdrv->sriov_set_msix_vec_count) {
+	if (!pdev->driver || !pdev->driver->sriov_set_msix_vec_count) {
 		ret = -EOPNOTSUPP;
 		goto err_pdev;
 	}
 
 	device_lock(&vf_dev->dev);
-	if (to_pci_driver(vf_dev->dev.driver)) {
+	if (vf_dev->driver) {
 		/*
 		 * A driver is already attached to this VF and has configured
 		 * itself based on the current MSI-X vector count. Changing
@@ -212,7 +208,7 @@ static ssize_t sriov_vf_msix_count_store(struct device *dev,
 		goto err_dev;
 	}
 
-	ret = pdrv->sriov_set_msix_vec_count(vf_dev, val);
+	ret = pdev->driver->sriov_set_msix_vec_count(vf_dev, val);
 
 err_dev:
 	device_unlock(&vf_dev->dev);
@@ -379,7 +375,6 @@ 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_driver *pdrv;
 	int ret = 0;
 	u16 num_vfs;
 
@@ -395,15 +390,14 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 		goto exit;
 
 	/* is PF driver loaded */
-	pdrv = to_pci_driver(dev->driver);
-	if (!pdrv) {
+	if (!pdev->driver) {
 		pci_info(pdev, "no driver bound to device; cannot configure SR-IOV\n");
 		ret = -ENOENT;
 		goto exit;
 	}
 
 	/* is PF driver loaded w/callback */
-	if (!pdrv->sriov_configure) {
+	if (!pdev->driver->sriov_configure) {
 		pci_info(pdev, "driver does not support SR-IOV configuration via sysfs\n");
 		ret = -ENOENT;
 		goto exit;
@@ -411,7 +405,7 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 
 	if (num_vfs == 0) {
 		/* disable VFs */
-		ret = pdrv->sriov_configure(pdev, 0);
+		ret = pdev->driver->sriov_configure(pdev, 0);
 		goto exit;
 	}
 
@@ -423,7 +417,7 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 		goto exit;
 	}
 
-	ret = pdrv->sriov_configure(pdev, num_vfs);
+	ret = pdev->driver->sriov_configure(pdev, num_vfs);
 	if (ret < 0)
 		goto exit;