linux-kernel - Re: [patch] drm/i915: fix a read size argument

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Date:   Thu, 13 Oct 2016 10:07:22 +0100
From:   Eric Engestrom <eric.engestrom@...tec.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
CC:     Daniel Vetter <daniel.vetter@...el.com>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        <intel-gfx@...ts.freedesktop.org>,
        <kernel-janitors@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>
Subject: Re: [patch] drm/i915: fix a read size argument

On Thu, Oct 13, 2016 at 11:55:08AM +0300, Dan Carpenter wrote:
> We want to read 3 bytes here, but because the parenthesis are in the
> wrong place we instead read:
> 
> 	sizeof(intel_dp->edp_dpcd) == sizeof(intel_dp->edp_dpcd)
> 
> which is one byte.
> 
> Fixes: fe5a66f91c88 ("drm/i915: Read PSR caps/intermediate freqs/etc. only once on eDP")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Good catch!  What tool did you use to find it, or did you find it by
inspection?
Reviewed-by: Eric Engestrom <eric.engestrom@...tec.com>

(btw, there's a missing `---` here, between the commit msg and the diff)

> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 14a3cf0..ee8aa95 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3551,8 +3551,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
>  	/* Read the eDP Display control capabilities registers */
>  	if ((intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
>  	    drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,
> -			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd) ==
> -			     sizeof(intel_dp->edp_dpcd)))
> +			     intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd)) ==
> +			     sizeof(intel_dp->edp_dpcd))
>  		DRM_DEBUG_KMS("EDP DPCD : %*ph\n", (int) sizeof(intel_dp->edp_dpcd),
>  			      intel_dp->edp_dpcd);