Patch "device-dax: fix cdev leak" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    device-dax: fix cdev leak

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     device-dax-fix-cdev-leak.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ed01e50acdd3e4a640cf9ebd28a7e810c3ceca97 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Fri, 17 Mar 2017 12:48:09 -0600
Subject: device-dax: fix cdev leak

From: Dan Williams <dan.j.williams@intel.com>

commit ed01e50acdd3e4a640cf9ebd28a7e810c3ceca97 upstream.

If device_add() fails, cleanup the cdev. Otherwise, we leak a kobj_map()
with a stale device number.

As Jason points out, there is a small possibility that userspace has
opened and mapped the device in the time between cdev_add() and the
device_add() failure. We need a new kill_dax_dev() helper to invalidate
any established mappings.

Fixes: ba09c01d2fa8 ("dax: convert to the cdev api")
Reported-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/dax/dax.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -553,13 +553,10 @@ static void dax_dev_release(struct devic
 	kfree(dax_dev);
 }
 
-static void unregister_dax_dev(void *dev)
+static void kill_dax_dev(struct dax_dev *dax_dev)
 {
-	struct dax_dev *dax_dev = to_dax_dev(dev);
 	struct cdev *cdev = &dax_dev->cdev;
 
-	dev_dbg(dev, "%s\n", __func__);
-
 	/*
 	 * Note, rcu is not protecting the liveness of dax_dev, rcu is
 	 * ensuring that any fault handlers that might have seen
@@ -571,6 +568,15 @@ static void unregister_dax_dev(void *dev
 	synchronize_srcu(&dax_srcu);
 	unmap_mapping_range(dax_dev->inode->i_mapping, 0, 0, 1);
 	cdev_del(cdev);
+}
+
+static void unregister_dax_dev(void *dev)
+{
+	struct dax_dev *dax_dev = to_dax_dev(dev);
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	kill_dax_dev(dax_dev);
 	device_unregister(dev);
 }
 
@@ -647,6 +653,7 @@ struct dax_dev *devm_create_dax_dev(stru
 	dev_set_name(dev, "dax%d.%d", dax_region->id, dax_dev->id);
 	rc = device_add(dev);
 	if (rc) {
+		kill_dax_dev(dax_dev);
 		put_device(dev);
 		return ERR_PTR(rc);
 	}


Patches currently in stable-queue which might be from dan.j.williams@intel.com are

queue-4.9/x86-pmem-fix-cache-flushing-for-iovec-write-8-bytes.patch
queue-4.9/device-dax-fix-cdev-leak.patch