linux-kernel - Re: [PATCH] drm/amd/display: invalid parameter check in dmub_hpd

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Date:   Mon, 10 Jan 2022 11:34:44 -0500
From:   Harry Wentland <harry.wentland@....com>
To:     José Expósito <jose.exposito89@...il.com>,
        shenshih@....com
Cc:     sunpeng.li@....com, Rodrigo.Siqueira@....com,
        alexander.deucher@....com, christian.koenig@....com,
        Xinhui.Pan@....com, airlied@...ux.ie, daniel@...ll.ch,
        nicholas.kazlauskas@....com, Anson.Jacob@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display: invalid parameter check in
 dmub_hpd_callback

On 2022-01-09 13:42, José Expósito wrote:
> The function performs a check on the "adev" input parameter, however, it
> is used before the check.
> 
> Initialize the "dev" variable after the sanity check to avoid a possible
> NULL pointer dereference.
> 
> Fixes: e27c41d5b0681 ("drm/amd/display: Support for DMUB HPD interrupt handling")
> Addresses-Coverity-ID: 1493909 ("Null pointer dereference")
> Signed-off-by: José Expósito <jose.exposito89@...il.com>

Reviewed-by: Harry Wentland <harry.wentland@....com>

Harry

> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index e727f1dd2a9a..7fbded7a6d9c 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -656,7 +656,7 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
>  	struct drm_connector_list_iter iter;
>  	struct dc_link *link;
>  	uint8_t link_index = 0;
> -	struct drm_device *dev = adev->dm.ddev;
> +	struct drm_device *dev;
>  
>  	if (adev == NULL)
>  		return;
> @@ -673,6 +673,7 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
>  
>  	link_index = notify->link_index;
>  	link = adev->dm.dc->links[link_index];
> +	dev = adev->dm.ddev;
>  
>  	drm_connector_list_iter_begin(dev, &iter);
>  	drm_for_each_connector_iter(connector, &iter) {