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PCI: Fix race condition with driver_override 

The driver_override implementation is susceptible to a race condition when
different threads are reading vs. storing a different driver override.  Add
locking to avoid the race condition.

This is in close analogy to commit 6265539776 ("driver core: platform:
fix race condition with driver_override") from Adrian Salido.

Fixes: 782a985d7a ("PCI: Introduce new device binding path using pci_dev.driver_override")
Signed-off-by: Nicolai Stange <nstange@suse.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org	# v3.16+
This commit is contained in:
Nicolai Stange 2017-09-11 09:45:40 +02:00 committed by Bjorn Helgaas
parent fe59493240
commit 9561475db6
1 changed files with 9 additions and 2 deletions
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11
drivers/pci/pci-sysfs.c
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@ -686,7 +686,7 @@ static ssize_t driver_override_store(struct device *dev,
const char *buf, size_t count)
{
struct pci_dev *pdev = to_pci_dev(dev);
char *driver_override, *old = pdev->driver_override, *cp;
char *driver_override, *old, *cp;
/* We need to keep extra room for a newline */
if (count >= (PAGE_SIZE - 1))
@ -700,12 +700,15 @@ static ssize_t driver_override_store(struct device *dev,
if (cp)
*cp = '\0';
device_lock(dev);
old = pdev->driver_override;
if (strlen(driver_override)) {
pdev->driver_override = driver_override;
} else {
kfree(driver_override);
pdev->driver_override = NULL;
}
device_unlock(dev);
kfree(old);
@ -716,8 +719,12 @@ static ssize_t driver_override_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct pci_dev *pdev = to_pci_dev(dev);
ssize_t len;
return snprintf(buf, PAGE_SIZE, "%s\n", pdev->driver_override);
device_lock(dev);
len = snprintf(buf, PAGE_SIZE, "%s\n", pdev->driver_override);
device_unlock(dev);
return len;
}
static DEVICE_ATTR_RW(driver_override);