linux-kernel - Re: [PATCH v3 4/6] tpm: TPM 2.0 sysfs attributes

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Date:	Thu, 16 Oct 2014 11:31:46 +0200
From:	Greg KH <greg@...ah.com>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:	Peter Huewe <peterhuewe@....de>, Ashley Lai <ashley@...leylai.com>,
	Marcel Selhorst <tpmdd@...horst.net>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org, josh.triplett@...el.com,
	christophe.ricard@...il.com, will.c.arthur@...el.com,
	monty.wiseman@...el.com
Subject: Re: [PATCH v3 4/6] tpm: TPM 2.0 sysfs attributes

On Wed, Oct 15, 2014 at 01:35:14PM +0200, Jarkko Sakkinen wrote:
> +int tpm2_sysfs_add_device(struct tpm_chip *chip)
> +{
> +	struct pcr_bank *pcr_bank;
> +	struct kobject *pcrs_kobj;
> +	struct device *dev = chip->dev;
> +	int rc;
> +
> +	rc = sysfs_create_group(&chip->vendor.miscdev.this_device->kobj,
> +				&tpm_dev_group);
> +	if (rc) {
> +		dev_err(dev, "failed to create sysfs attributes, %d\n", rc);
> +		return rc;
> +	}

You just raced and created sysfs files _after_ userspace saw that your
device was enabled.

> +	pcrs_kobj = kobject_create_and_add("pcrs",
> +					   &chip->vendor.miscdev.this_device->kobj);

Ick, no no no no.  Never create a kobject under a 'struct device'.  You
just lost all libudev support for any attribute you created under here,
not good at all.  Use a "real" device if you really want a sub-device,
not a kobject.

thanks,

greg k-h
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