Re: [PATCH 2/2] drm/dp: Don't trust drm_dp_downstream_id()

From: Jani Nikula <jani.nikula@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 2/2] drm/dp: Don't trust drm_dp_downstream_id()
Date: Fri, 21 Jul 2017 10:22:27 +0300	[thread overview]
Message-ID: <874lu6ntjg.fsf@intel.com> (raw)
In-Reply-To: <20170720174532.23377-2-chris@chris-wilson.co.uk>

On Thu, 20 Jul 2017, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> Before we interpret drm_dp_downstream_id() as a string, make sure it is
> NULL terminated, even when drm_dp_downtsream_id() fails.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101660
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 1d9e30f0dbf8..08af8d6b844b 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -544,7 +544,7 @@ void drm_dp_downstream_debug(struct seq_file *m,
>  				 DP_DETAILED_CAP_INFO_AVAILABLE;
>  	int clk;
>  	int bpc;
> -	char id[6];
> +	char id[7];
>  	int len;
>  	uint8_t rev[2];
>  	int type = port_cap[0] & DP_DS_PORT_TYPE_MASK;
> @@ -583,6 +583,7 @@ void drm_dp_downstream_debug(struct seq_file *m,
>  		seq_puts(m, "\t\tType: N/A\n");
>  	}
>  
> +	memset(id, 0, sizeof(id));
>  	drm_dp_downstream_id(aux, id);
>  	seq_printf(m, "\t\tID: %s\n", id);

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

although I'd probably have gone for checking the return value of
drm_dp_downstream_id() and using %*pE format with strnlen for the
length.

-- 
Jani Nikula, Intel Open Source Technology Center
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