linux-kernel - Re: [PATCH] nvme: pci: Fix NULL dereference when resetting NVMe SSD

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Message-ID: <20170522160217.GA26104@lst.de>
Date:   Mon, 22 May 2017 18:02:17 +0200
From:   Christoph Hellwig <hch@....de>
To:     Rakesh Pandit <rakesh@...era.com>
Cc:     Christoph Hellwig <hch@....de>, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Keith Busch <keith.busch@...el.com>,
        Jens Axboe <axboe@...com>, Sagi Grimberg <sagi@...mberg.me>,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH] nvme: pci: Fix NULL dereference when resetting NVMe SSD

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?

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b01bd5bba8e6..f8c15e2719c4 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;
 
+	device_lock(&dev->dev);
 	pci_dev_save_and_disable(dev);
 
-	rc = pci_dev_reset(dev, 0);
+	rc = __pci_dev_reset(dev, 0);
 
 	pci_dev_restore(dev);
+	device_unlock(&dev->dev);
 
 	return rc;
 }