Re: [PATCH] drm/display: fix possible null-pointer dereference in dcn10_set_clock()

[Tuo Li <islituo@gmail.com>]

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Thanks for your feedback. We will prepare a V2 patch according to your advice.

Best wishes,
Tuo Li


On 2021/8/10 21:38, Chen, Guchun wrote:
> [Public]
>
> Thanks for your patch.
>
> I suggest moving the check of function pointer dc->clk_mgr->funcs->get_clock earlier, and return early if it's NULL, as if it's NULL, it's meaningless to continue the clock setting.
>
> ....
> if (!dc->clk_mgr || !dc->clk_mgr->funcs->get_clock)
>   	return DC_FAIL_UNSUPPORTED_1;
>
> dc->clk_mgr->funcs->get_clock(dc->clk_mgr,
>   	context, clock_type, &clock_cfg);
> ....
>
> Regards,
> Guchun
>
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of Tuo Li
> Sent: Tuesday, August 10, 2021 5:20 PM
> To: Wentland, Harry <Harry.Wentland@amd.com>; Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; airlied@linux.ie; daniel@ffwll.ch; Cyr, Aric <Aric.Cyr@amd.com>; Lei, Jun <Jun.Lei@amd.com>; Zhuo, Qingqing <Qingqing.Zhuo@amd.com>; Siqueira, Rodrigo <Rodrigo.Siqueira@amd.com>; Lee, Alvin <Alvin.Lee2@amd.com>; Stempen, Vladimir <Vladimir.Stempen@amd.com>; isabel.zhang@amd.com; Lee, Sung <Sung.Lee@amd.com>; Po-Yu Hsieh Paul <Paul.Hsieh@amd.com>; Wood, Wyatt <Wyatt.Wood@amd.com>
> Cc: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; baijiaju1990@gmail.com; Tuo Li <islituo@gmail.com>; TOTE Robot <oslab@tsinghua.edu.cn>
> Subject: [PATCH] drm/display: fix possible null-pointer dereference in dcn10_set_clock()
>
> The variable dc->clk_mgr is checked in:
>    if (dc->clk_mgr && dc->clk_mgr->funcs->get_clock)
>
> This indicates dc->clk_mgr can be NULL.
> However, it is dereferenced in:
>    if (!dc->clk_mgr->funcs->get_clock)
>
> To fix this possible null-pointer dereference, check dc->clk_mgr before dereferencing it.
>
> Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
> Signed-off-by: Tuo Li <islituo@gmail.com>
> ---
>   drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
> index c545eddabdcc..3a7c7c7efa68 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
> @@ -3635,7 +3635,7 @@ enum dc_status dcn10_set_clock(struct dc *dc,
>   				dc->clk_mgr->funcs->get_clock(dc->clk_mgr,
>   						context, clock_type, &clock_cfg);
>   
> -	if (!dc->clk_mgr->funcs->get_clock)
> +	if (dc->clk_mgr && !dc->clk_mgr->funcs->get_clock)
>   		return DC_FAIL_UNSUPPORTED_1;
>   
>   	if (clk_khz > clock_cfg.max_clock_khz)
> --
> 2.25.1


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