linux-kernel - Re: [PATCH 1/2] tpm/tpm_ibmvtpm: Fail in ibmvtpm_get_data if driver

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Message-ID: <alpine.DEB.2.10.1409221219150.4510@ant>
Date:	Mon, 22 Sep 2014 12:43:27 -0500 (CDT)
From:	Ashley Lai <ashley@...leylai.com>
To:	Anton Blanchard <anton@...ba.org>
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
Subject: Re: [PATCH 1/2] tpm/tpm_ibmvtpm: Fail in ibmvtpm_get_data if
 driver_data is bad

Hi Anton,

Thanks for the patch.  Is this oops easy to recreate?  If so could 
you give us the steps to reproduce?

Thanks,
--Ashley Lai

On Sat, 20 Sep 2014, Anton Blanchard wrote:

> I'm looking at an oops in tpm_ibmvtpm_get_desired_dma:
>
>  28:	00 00 20 39 	li      r9,0
>  2c:	10 00 01 e8 	ld      r0,16(r1)
>  30:	28 00 69 80 	lwz     r3,40(r9)
>
> We set r9 to 0 then load r9+40. The problem is actually in
> ibmvtpm_get_data, it can return NULL but the rest of the driver
> never expects it.
>
> Add a BUG_ON in ibmvtpm_get_data. We still need to identify the root
> cause but at least this makes it obvious what went wrong.
>
> Cc: stable@...r.kernel.org
> Signed-off-by: Anton Blanchard <anton@...ba.org>
> ---
>
> diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
> index af74c57..0d1eeba 100644
> --- a/drivers/char/tpm/tpm_ibmvtpm.c
> +++ b/drivers/char/tpm/tpm_ibmvtpm.c
> @@ -63,9 +63,9 @@ static int ibmvtpm_send_crq(struct vio_dev *vdev, u64 w1, u64 w2)
> static struct ibmvtpm_dev *ibmvtpm_get_data(const struct device *dev)
> {
> 	struct tpm_chip *chip = dev_get_drvdata(dev);
> -	if (chip)
> -		return (struct ibmvtpm_dev *)TPM_VPRIV(chip);
> -	return NULL;
> +
> +	BUG_ON(!chip);
> +	return (struct ibmvtpm_dev *)TPM_VPRIV(chip);
> }
>
> /**
>
--
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