[PATCH v2] drm/amd/display: Add NULL check for clk_mgr and clk_mgr->funcs in dcn30_init_hw

[Alex Hung]

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

On 2024-07-22 04:51, Srinivasan Shanmugam wrote:
> This commit addresses a potential null pointer dereference issue in the
> `dcn30_init_hw` function. The issue could occur when `dc->clk_mgr` or
> `dc->clk_mgr->funcs` is null.
> 
> The fix adds a check to ensure `dc->clk_mgr` and `dc->clk_mgr->funcs` is
> not null before accessing its functions. This prevents a potential null
> pointer dereference.
> 
> Reported by smatch:
> drivers/gpu/drm/amd/amdgpu/../display/dc/hwss/dcn30/dcn30_hwseq.c:789 dcn30_init_hw() error: we previously assumed 'dc->clk_mgr' could be null (see line 628)
> 
> Cc: Tom Chung <chiahsuan.chung at amd.com>
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
> Cc: Roman Li <roman.li at amd.com>
> Cc: Alex Hung <alex.hung at amd.com>
> Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
> Cc: Harry Wentland <harry.wentland at amd.com>
> Cc: Hamza Mahfooz <hamza.mahfooz at amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
> ---
> v2: Along with "dc->clk_mgr" add check for even dc->clk_mgr->funcs" (Tom)
> 
>   drivers/gpu/drm/amd/display/dc/hwss/dcn30/dcn30_hwseq.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn30/dcn30_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn30/dcn30_hwseq.c
> index fc5936460ac2..98a40d46aaae 100644
> --- a/drivers/gpu/drm/amd/display/dc/hwss/dcn30/dcn30_hwseq.c
> +++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn30/dcn30_hwseq.c
> @@ -625,7 +625,7 @@ void dcn30_init_hw(struct dc *dc)
>   	uint32_t backlight = MAX_BACKLIGHT_LEVEL;
>   	uint32_t user_level = MAX_BACKLIGHT_LEVEL;
>   
> -	if (dc->clk_mgr && dc->clk_mgr->funcs->init_clocks)
> +	if (dc->clk_mgr && dc->clk_mgr->funcs && dc->clk_mgr->funcs->init_clocks)
>   		dc->clk_mgr->funcs->init_clocks(dc->clk_mgr);
>   
>   	// Initialize the dccg
> @@ -786,11 +786,12 @@ void dcn30_init_hw(struct dc *dc)
>   	if (!dcb->funcs->is_accelerated_mode(dcb) && dc->res_pool->hubbub->funcs->init_watermarks)
>   		dc->res_pool->hubbub->funcs->init_watermarks(dc->res_pool->hubbub);
>   
> -	if (dc->clk_mgr->funcs->notify_wm_ranges)
> +	if (dc->clk_mgr && dc->clk_mgr->funcs && dc->clk_mgr->funcs->notify_wm_ranges)
>   		dc->clk_mgr->funcs->notify_wm_ranges(dc->clk_mgr);
>   
>   	//if softmax is enabled then hardmax will be set by a different call
> -	if (dc->clk_mgr->funcs->set_hard_max_memclk && !dc->clk_mgr->dc_mode_softmax_enabled)
> +	if (dc->clk_mgr && dc->clk_mgr->funcs && dc->clk_mgr->funcs->set_hard_max_memclk &&
> +	    !dc->clk_mgr->dc_mode_softmax_enabled)
>   		dc->clk_mgr->funcs->set_hard_max_memclk(dc->clk_mgr);
>   
>   	if (dc->res_pool->hubbub->funcs->force_pstate_change_control)