linux-kernel - Re: [PATCH] drm/amd/display: Add null pointer check in mod_hdcp_hdcp1_create

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Message-ID: <647d318e-b0f7-436d-84b1-eae2687932d4@amd.com>
Date: Sun, 17 Aug 2025 17:57:50 -0600
From: Alex Hung <alex.hung@....com>
To: Chenyuan Yang <chenyuan0y@...il.com>, harry.wentland@....com,
 sunpeng.li@....com
Cc: siqueira@...lia.com, alexander.deucher@....com, christian.koenig@....com,
 airlied@...il.com, simona@...ll.ch, vulab@...as.ac.cn, Wenjing.Liu@....com,
 isabel.zhang@....com, amd-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display: Add null pointer check in
 mod_hdcp_hdcp1_create_session()

Reviewed-by: Alex Hung <alex.hung@....com>

On 7/23/25 20:36, Chenyuan Yang wrote:
> The function mod_hdcp_hdcp1_create_session() calls the function
> get_first_active_display(), but does not check its return value.
> The return value is a null pointer if the display list is empty.
> This will lead to a null pointer dereference.
> 
> Add a null pointer check for get_first_active_display() and return
> MOD_HDCP_STATUS_DISPLAY_NOT_FOUND if the function return null.
> 
> This is similar to the commit c3e9826a2202
> ("drm/amd/display: Add null pointer check for get_first_active_display()").
> 
> Fixes: 2deade5ede56 ("drm/amd/display: Remove hdcp display state with mst fix")
> Signed-off-by: Chenyuan Yang <chenyuan0y@...il.com>
> ---
>   drivers/gpu/drm/amd/display/modules/hdcp/hdcp_psp.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_psp.c b/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_psp.c
> index e58e7b93810b..6b7db8ec9a53 100644
> --- a/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_psp.c
> +++ b/drivers/gpu/drm/amd/display/modules/hdcp/hdcp_psp.c
> @@ -260,6 +260,9 @@ enum mod_hdcp_status mod_hdcp_hdcp1_create_session(struct mod_hdcp *hdcp)
>   		return MOD_HDCP_STATUS_FAILURE;
>   	}
>   
> +	if (!display)
> +		return MOD_HDCP_STATUS_DISPLAY_NOT_FOUND;
> +
>   	hdcp_cmd = (struct ta_hdcp_shared_memory *)psp->hdcp_context.context.mem_context.shared_buf;
>   
>   	mutex_lock(&psp->hdcp_context.mutex);