Re: [PATCH] drm/amd/display: Fix NULL deref in dcn401_update_clocks_update_dtb_dto

[Alex Hung <alex.hung@amd.com>]

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

On 10/19/26 01:29, Roman Demidov wrote:
> [Why]
> resource_get_otg_master_for_stream() can return NULL if no OTG master pipe
> is found for a given stream. The current code dereferences this pointer
> without a NULL check. This may lead to a possible NULL pointer
> dereference.
> 
> [How]
> Add an explicit NULL check and skip the stream if the OTG master is not
> found. This is similar to dcn60_update_clocks_update_dtb_dto().
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: b6d508533fa1 ("drm/amd/display: fix a crash when clock source is reference for non otg master pipe")
> Signed-off-by: Roman Demidov <roman.demidov.nn@gmail.com>
> ---
>   drivers/gpu/drm/amd/display/dc/clk_mgr/dcn401/dcn401_clk_mgr.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn401/dcn401_clk_mgr.c b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn401/dcn401_clk_mgr.c
> index 6ee3da89d058..135eeef68ac4 100644
> --- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn401/dcn401_clk_mgr.c
> +++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn401/dcn401_clk_mgr.c
> @@ -538,6 +538,9 @@ static void dcn401_update_clocks_update_dtb_dto(struct clk_mgr_internal *clk_mgr
>   		otg_master = resource_get_otg_master_for_stream(
>   				&context->res_ctx, context->streams[i]);
>   		ASSERT(otg_master);
> +		if (!otg_master)
> +			continue;
> +
>   		ASSERT(otg_master->clock_source);
>   		ASSERT(otg_master->clock_source->funcs->program_pix_clk);
>   		ASSERT(otg_master->stream_res.pix_clk_params.controller_id >= CONTROLLER_ID_D0);