linux-kernel - Re: [PATCH] tpm: fix compat 'ppi' link handling in tpm_chip

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Date:	Mon, 9 Nov 2015 22:11:41 -0800
From:	Jeremiah Mahler <jmmahler@...il.com>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	"moderated list:TPM DEVICE DRIVER" 
	<tpmdd-devel@...ts.sourceforge.net>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: fix compat 'ppi' link handling in
 tpm_chip_register()

Jarkko,

On Sun, Nov 08, 2015 at 09:51:07AM +0200, Jarkko Sakkinen wrote:
> __compat_only_sysfs_link_entry_to_kobj() was unconditionally called for
> TPM1 chips, which caused crash on Acer C720 laptop where DSM for the
> ACPI object did not exist.
> 
> There are two reasons for unwanted behavior:
> 
> * The code did not check whether
>   __compat_only_sysfs_link_entry_to_kobj() returned -ENOENT. This is
>   OK. It just meanst that ppi is not available.
> * The code did not clean up properly. Compat link should added only
>   after all other init is done.
> 
> This patch sorts out these issues.
> 
> Fixes: 9b774d5cf2db
> Reported-by: Jeremiah Mahler <jmmahler@...il.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> Tested-by: Jeremiah Mahler <jmmahler@...il.com>
> ---
>  drivers/char/tpm/tpm-chip.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index a5cdce7..45cc39a 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -226,14 +226,6 @@ int tpm_chip_register(struct tpm_chip *chip)
>  	if (rc)
>  		goto out_err;
>  
> -	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
> -		rc = __compat_only_sysfs_link_entry_to_kobj(&chip->pdev->kobj,
> -							    &chip->dev.kobj,
> -							    "ppi");
> -		if (rc)
> -			goto out_err;
> -	}
> -
>  	/* Make the chip available. */
>  	spin_lock(&driver_lock);
>  	list_add_tail_rcu(&chip->list, &tpm_chip_list);
> @@ -241,6 +233,16 @@ int tpm_chip_register(struct tpm_chip *chip)
>  
>  	chip->flags |= TPM_CHIP_FLAG_REGISTERED;
>  
> +	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
> +		rc = __compat_only_sysfs_link_entry_to_kobj(&chip->pdev->kobj,
> +							    &chip->dev.kobj,
> +							    "ppi");
> +		if (rc && rc != -ENOENT) {
> +			tpm_chip_unregister(chip);
> +			return rc;
> +		}
> +	}
> +
>  	return 0;
>  out_err:
>  	tpm1_chip_unregister(chip);
> -- 
> 2.5.0
> 

This patch doesn't apply to the latest linux-next (20151109).  I think I
may be missing a dependent patch.  Do you know which one?

-- 
- Jeremiah Mahler
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