linux-kernel - Re: [PATCH] driver/char/tpm: fix regression causesd by ppi

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Message-ID: <20121009221848.GA17467@ennui.austin.ibm.com>
Date:	Tue, 9 Oct 2012 17:18:50 -0500
From:	Kent Yoder <key@...ux.vnet.ibm.com>
To:	gang.wei@...el.com
Cc:	key@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	tpmdd-devel@...ts.sourceforge.net,
	linux-security-module@...r.kernel.org, james.l.morris@...cle.com,
	ebiederm@...ssion.com, ben@...hro.net
Subject: Re: [PATCH] driver/char/tpm: fix regression causesd by ppi

Hi Jimmy,

On Tue, Oct 09, 2012 at 05:35:22PM +0800, gang.wei@...el.com wrote:
> From: Gang Wei <gang.wei@...el.com>
> 
> This patch try to fix the S3 regression https://lkml.org/lkml/2012/10/5/433,
> which includes below line:
> [ 1554.684638] sysfs: cannot create duplicate filename '/devices/pnp0/00:0c/ppi'
> 
> The root cause is that ppi sysfs teardown code is MIA, so while S3 resume,
> the ppi kobject will be created again upon existing one.
> 
> To make the tear down code simple, change the ppi subfolder creation from
> using kobject_create_and_add to just using a named ppi attribute_group. Then
> ppi sysfs teardown could be done with a simple sysfs_remove_group call.
> 
> Adjusted the name & return type for ppi sysfs init function.
> 
> Reported-by: Ben Guthro <ben@...hro.net>
> Signed-off-by: Gang Wei <gang.wei@...el.com>
> ---
>  drivers/char/tpm/tpm.c     |    3 ++-
>  drivers/char/tpm/tpm.h     |    9 +++++++--
>  drivers/char/tpm/tpm_ppi.c |   18 ++++++++++--------
>  3 files changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
> index f26afdb..b429f1e 100644
> --- a/drivers/char/tpm/tpm.c
> +++ b/drivers/char/tpm/tpm.c
> @@ -1259,6 +1259,7 @@ void tpm_remove_hardware(struct device *dev)
> 
>  	misc_deregister(&chip->vendor.miscdev);
>  	sysfs_remove_group(&dev->kobj, chip->vendor.attr_group);
> +	tpm_remove_ppi(&dev->kobj);
>  	tpm_bios_log_teardown(chip->bios_dir);
> 
>  	/* write it this way to be explicit (chip->dev == dev) */
> @@ -1476,7 +1477,7 @@ struct tpm_chip *tpm_register_hardware(struct device *dev,
>  		goto put_device;
>  	}
> 
> -	if (sys_add_ppi(&dev->kobj)) {
> +	if (tpm_add_ppi(&dev->kobj)) {
>  		misc_deregister(&chip->vendor.miscdev);
>  		goto put_device;
>  	}

  Hmm, tpm_add_ppi is just sysfs_create_group, which only ever returns
0. Looks like we can remove this error path, but PPI is unusable in the
failure case.

> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 02c266a..8ef7649 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -329,10 +329,15 @@ extern int wait_for_tpm_stat(struct tpm_chip *, u8, unsigned long,
>  			     wait_queue_head_t *);
> 
>  #ifdef CONFIG_ACPI
> -extern ssize_t sys_add_ppi(struct kobject *parent);
> +extern int tpm_add_ppi(struct kobject *);
> +extern void tpm_remove_ppi(struct kobject *);
>  #else
> -static inline ssize_t sys_add_ppi(struct kobject *parent)
> +static inline int tpm_add_ppi(struct kobject *parent)
>  {
>  	return 0;
>  }
> +
> +static inline void tpm_remove_ppi(struct kobject *parent)
> +{
> +}
>  #endif
> diff --git a/drivers/char/tpm/tpm_ppi.c b/drivers/char/tpm/tpm_ppi.c
> index f27b58c..720ebcf 100644
> --- a/drivers/char/tpm/tpm_ppi.c
> +++ b/drivers/char/tpm/tpm_ppi.c
> @@ -444,18 +444,20 @@ static struct attribute *ppi_attrs[] = {
>  	&dev_attr_vs_operations.attr, NULL,
>  };
>  static struct attribute_group ppi_attr_grp = {
> +	.name = "ppi",
>  	.attrs = ppi_attrs
>  };
> 
> -ssize_t sys_add_ppi(struct kobject *parent)
> +int tpm_add_ppi(struct kobject *parent)
>  {
> -	struct kobject *ppi;
> -	ppi = kobject_create_and_add("ppi", parent);
> -	if (sysfs_create_group(ppi, &ppi_attr_grp))
> -		return -EFAULT;
> -	else
> -		return 0;
> +	return sysfs_create_group(parent, &ppi_attr_grp);
> +}
> +EXPORT_SYMBOL_GPL(tpm_add_ppi);
> +
> +void tpm_remove_ppi(struct kobject *parent)
> +{
> +	sysfs_remove_group(parent, &ppi_attr_grp);
>  }
> -EXPORT_SYMBOL_GPL(sys_add_ppi);
> +EXPORT_SYMBOL_GPL(tpm_remove_ppi);

 Do we need to export these symbols?  These might have been left around
from when ppi was a standalone module.

Kent

>  MODULE_LICENSE("GPL");
> -- 
> 1.7.7.6
> 

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