linux-kernel - Re: [PATCH 1/3] tpm: Hold the kref during tpm_chip_find

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Message-ID: <20160214045512.GA7777@intel.com>
Date:	Sun, 14 Feb 2016 06:55:12 +0200
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	Stefan Berger <stefanb@...ibm.com>,
	Peter Huewe <peterhuewe@....de>
Subject: Re: [PATCH 1/3] tpm: Hold the kref during tpm_chip_find_get

On Fri, Feb 12, 2016 at 05:04:29PM -0700, Jason Gunthorpe wrote:
> This was missed during the struct device conversion, we
> need to hold a kref on the chip to make sure it isn't freed.
> 
> Signed-off-by: Jason Gunthorpe <jgunthorpe@...idianresearch.com>

I'm bit confused about this patch. What is the regression if this needs
to be dropped from my last pull request for 4.5 (that is the only one
I'm planning to include from this patch set, rest are definitely
post-4.5)?

If there is clear regression in this patch, I can do it. I didn't
reproduce any.

/Jarkko

> ---
>  drivers/char/tpm/tpm-chip.c | 2 ++
>  drivers/char/tpm/tpm.h      | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 45cc39aabeee..ae2fed8a162b 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -53,6 +53,8 @@ struct tpm_chip *tpm_chip_find_get(int chip_num)
>  			chip = pos;
>  			break;
>  		}
> +
> +		get_device(&chip->dev);
>  	}
>  	rcu_read_unlock();
>  	return chip;
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 542a80cbfd9c..f6ba79d91857 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -207,6 +207,7 @@ struct tpm_chip {
>  static inline void tpm_chip_put(struct tpm_chip *chip)
>  {
>  	module_put(chip->pdev->driver->owner);
> +	put_device(&chip->dev);
>  }
>  
>  static inline int tpm_read_index(int base, int index)
> -- 
> 2.1.4
>