[PATCH] nvme: pci: Fix NULL dereference when resetting NVMe SSD

[Christoph Hellwig]

On Mon, May 22, 2017 at 06:02:17PM +0200, Christoph Hellwig wrote:
> On Mon, May 22, 2017 at 06:38:29PM +0300, Rakesh Pandit wrote:
> > Just got to use the using the test box again and you are right that
> > nvme_remove_dead_ctrl_work is getting called just before the NULL
> > pointer dereference.
> > 
> > Here call trace to nvme_timeout which results in eventually call to
> > nvme_reset when it wants to reset the controller (which races with
> > ->reset_notify from PCI layer):
> 
> Does the patch below fix the issue for you?

Actually, it probably should be this one, but for you the effects
are probably the same:

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b01bd5bba8e6..b61ad77dc322 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4275,11 +4275,13 @@ 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;
 }