[PATCH 4.14 088/246] PCI: Prevent sysfs disable of device while driver is attached

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Christoph Hellwig <h...@lst.de>

[ Upstream commit 6f5cdfa802733dcb561bf664cc89d203f2fd958f ]

Manipulating the enable_cnt behind the back of the driver will wreak
complete havoc with the kernel state, so disallow it.

Signed-off-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Bjorn Helgaas <bhelg...@google.com>
Reviewed-by: Johannes Thumshirn <jthumsh...@suse.de>
Acked-by: Keith Busch <keith.bu...@intel.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/pci/pci-sysfs.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -305,13 +305,16 @@ static ssize_t enable_store(struct devic
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
 
-       if (!val) {
-               if (pci_is_enabled(pdev))
-                       pci_disable_device(pdev);
-               else
-                       result = -EIO;
-       } else
+       device_lock(dev);
+       if (dev->driver)
+               result = -EBUSY;
+       else if (val)
                result = pci_enable_device(pdev);
+       else if (pci_is_enabled(pdev))
+               pci_disable_device(pdev);
+       else
+               result = -EIO;
+       device_unlock(dev);
 
        return result < 0 ? result : count;
 }