linux-kernel - Re: [PATCH] device-dax: fix cdev leak

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Date:   Thu, 23 Feb 2017 13:20:30 -0700
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm@...1.01.org, Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] device-dax: fix cdev leak

On Thu, Feb 23, 2017 at 11:22:03AM -0800, Dan Williams wrote:
> If device_add() fails, cleanup the cdev. Otherwise, we leak a kobj_map()
> with a stale device number.
> 
> Fixes: ba09c01d2fa8 ("dax: convert to the cdev api")
> Cc: <stable@...r.kernel.org>
> Cc: Logan Gunthorpe <logang@...tatee.com>
> Reported-by: Jason Gunthorpe <jgunthorpe@...idianresearch.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>  drivers/dax/dax.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
> index ed758b74ddf0..0f8008dd0b0c 100644
> +++ b/drivers/dax/dax.c
> @@ -724,6 +724,7 @@ 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) {
> +		cdev_del(&dax_dev->cdev);

This probably should call into unregister_dax_dev and just skip the
device_unregister part.

Once cdev_add returns it is possible for a mmap to have been created,
so cleanup after that point has to go through all the other
unregister_dax_dev steps.

Jason