On Mon, Sep 11, 2017 at 09:45:40AM +0200, Nicolai Stange wrote:
> 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")
> Cc: stable@xxxxxxxxxxxxxxx # v3.16+
> Signed-off-by: Nicolai Stange <nstange@xxxxxxx>
Applied to for-linus for v4.14, thanks!
> ---
> drivers/pci/pci-sysfs.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 1eecfa301f7f..8e075ea2743e 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -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);
>
> --
> 2.13.5
>
