PCI: Protect pci_error_handlers->reset_notify() usage with device_lock()

Every method in struct device_driver or structures derived from it like
struct pci_driver MUST provide exclusion vs the driver's ->remove() method,
usually by using device_lock().

Protect use of pci_error_handlers->reset_notify() by holding the device
lock while calling it.

Note:

  - pci_dev_lock() calls device_lock() in addition to blocking user-space
    config accesses.

  - pci_err_handlers->reset_notify() is used inside
    pci_dev_save_and_disable() and pci_dev_restore().  We could hold the
    device lock directly in pci_reset_notify(), but we expand the region
    since we have several calls following each other.

Without this, ->reset_notify() may race with ->remove() calls, which can be
easily triggered in NVMe.

[bhelgaas: changelog, add pci_reset_notify() comment]
[bhelgaas: fold in fix from Dan Carpenter <dan.carpenter@oracle.com>:
http://lkml.kernel.org/r/20170701135323.x5vaj4e2wcs2mcro@mwanda]
Link: http://lkml.kernel.org/r/20170601111039.8913-2-hch@lst.de
Reported-by: Rakesh Pandit <rakesh@tuxera.com>
Tested-by: Rakesh Pandit <rakesh@tuxera.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 3b38e98..f4587f6 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4143,6 +4143,12 @@ static void pci_reset_notify(struct pci_dev *dev, bool prepare)
 {
        const struct pci_error_handlers *err_handler =
                        dev->driver ? dev->driver->err_handler : NULL;
+
+       /*
+        * dev->driver->err_handler->reset_notify() is protected against
+        * races with ->remove() by the device lock, which must be held by
+        * the caller.
+        */
        if (err_handler && err_handler->reset_notify)
                err_handler->reset_notify(dev, prepare);
 }
@@ -4278,11 +4284,13 @@ int pci_reset_function(struct pci_dev *dev)
        if (rc)
                return rc;
 
+       pci_dev_lock(dev);
        pci_dev_save_and_disable(dev);
 
-       rc = pci_dev_reset(dev, 0);
+       rc = __pci_dev_reset(dev, 0);
 
        pci_dev_restore(dev);
+       pci_dev_unlock(dev);
 
        return rc;
 }
@@ -4302,16 +4310,14 @@ int pci_try_reset_function(struct pci_dev *dev)
        if (rc)
                return rc;
 
-       pci_dev_save_and_disable(dev);
+       if (!pci_dev_trylock(dev))
+               return -EAGAIN;
 
-       if (pci_dev_trylock(dev)) {
-               rc = __pci_dev_reset(dev, 0);
-               pci_dev_unlock(dev);
-       } else
-               rc = -EAGAIN;
+       pci_dev_save_and_disable(dev);
+       rc = __pci_dev_reset(dev, 0);
+       pci_dev_unlock(dev);
 
        pci_dev_restore(dev);
-
        return rc;
 }
 EXPORT_SYMBOL_GPL(pci_try_reset_function);
@@ -4461,7 +4467,9 @@ static void pci_bus_save_and_disable(struct pci_bus *bus)
        struct pci_dev *dev;
 
        list_for_each_entry(dev, &bus->devices, bus_list) {
+               pci_dev_lock(dev);
                pci_dev_save_and_disable(dev);
+               pci_dev_unlock(dev);
                if (dev->subordinate)
                        pci_bus_save_and_disable(dev->subordinate);
        }
@@ -4476,7 +4484,9 @@ static void pci_bus_restore(struct pci_bus *bus)
        struct pci_dev *dev;
 
        list_for_each_entry(dev, &bus->devices, bus_list) {
+               pci_dev_lock(dev);
                pci_dev_restore(dev);
+               pci_dev_unlock(dev);
                if (dev->subordinate)
                        pci_bus_restore(dev->subordinate);
        }