linux-kernel - Re: [PATCH] tpm_crb: check for bad response size

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Date:   Sat, 11 Mar 2017 10:48:06 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jerry Snitselaar <jsnitsel@...hat.com>
Cc:     tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Subject: Re: [PATCH] tpm_crb: check for bad response size

On Fri, Mar 10, 2017 at 05:46:04PM -0700, Jerry Snitselaar wrote:
> Make sure size of response buffer is at least 6 bytes, or
> we will underflow and pass large size_t to memcpy_fromio().
> This was encountered while testing earlier version of
> locality patchset.
> 
> Fixes: 30fc8d138e912 ("tpm: TPM 2.0 CRB Interface")
> Signed-off-by: Jerry Snitselaar <jsnitsel@...hat.com>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

/Jarkko

> ---
>  drivers/char/tpm/tpm_crb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> index 89dc8a176ff1..cda4f312d1c9 100644
> --- a/drivers/char/tpm/tpm_crb.c
> +++ b/drivers/char/tpm/tpm_crb.c
> @@ -236,7 +236,7 @@ static int crb_recv(struct tpm_chip *chip, u8 *buf, size_t count)
>  
>  	memcpy_fromio(buf, priv->rsp, 6);
>  	expected = be32_to_cpup((__be32 *) &buf[2]);
> -	if (expected > count)
> +	if (expected > count || expected < 6)
>  		return -EIO;
>  
>  	memcpy_fromio(&buf[6], &priv->rsp[6], expected - 6);
> -- 
> 2.11.0.258.ge05806da9
>