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Subject[PATCH 3.18 20/24] PCI: Fix race condition with driver_override
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicolai Stange <nstange@suse.de>

commit 9561475db680f7144d2223a409dd3d7e322aca03 upstream.

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 6265539776a0 ("driver core: platform:
fix race condition with driver_override") from Adrian Salido.

Fixes: 782a985d7af2 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/pci/pci-sysfs.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -513,7 +513,7 @@ static ssize_t driver_override_store(str
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))
@@ -527,12 +527,15 @@ static ssize_t driver_override_store(str
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);

@@ -543,8 +546,12 @@ static ssize_t driver_override_show(stru
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);


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