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patch "device-dax: fix cdev leak" added to char-misc-next

PATCH [email protected] 1 participant 1 message Mar 21, 2017

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

device-dax: fix cdev leak

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

Quoted 1 line

From ed01e50acdd3e4a640cf9ebd28a7e810c3ceca97 Mon Sep 17 00:00:00 2001

From: Dan Williams <[email protected]>
Date: Fri, 17 Mar 2017 12:48:09 -0600
Subject: device-dax: fix cdev leak

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")
Cc <[email protected]>
Reported-by Jason Gunthorpe <[email protected]>
Signed-off-by Dan Williams <[email protected]>
Signed-off-by Logan Gunthorpe <[email protected]>
Reviewed-by Johannes Thumshirn <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/dax/dax.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)
drivers/dax/dax.c +11 -4
index 8d9829ff2a78..a5ed59a5a968 100644
@@ -675,13 +675,10 @@ static void dax_dev_release(struct device *dev)
 	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

@@ -693,6 +690,15 @@ static void unregister_dax_dev(void *dev)
 	synchronize_rcu();
 	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);
 }
 

@@ -769,6 +775,7 @@ struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
 	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);
 	}
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