linux-kernel - Re: [PATCH RFC v2 5/5] tpm2: expose resource manager via a device link /dev/tpms<n>

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Date:   Thu, 12 Jan 2017 11:39:19 -0700
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     tpmdd-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 5/5] tpm2: expose resource manager via a device
 link /dev/tpms<n>

On Thu, Jan 12, 2017 at 07:46:08PM +0200, Jarkko Sakkinen wrote:

>  struct tpm_chip {
> -	struct device dev;
> -	struct cdev cdev;
> +	struct device dev, devrm;

Hum.. devrm adds a new kref but doesn't do anything with the release
function, so that is going to use after free, ie here:

> 	put_device(&chip->dev);
>+	put_device(&chip->devrm);
> 	return ERR_PTR(rc);

And other places.

One solution is to get_device(chip->dev) after
device_initialize(dev->rm) and add a devrm->dev.release function to
do put_device(chip->dev)

Jason