Re: [PATCH 6.1.y/6.6.y] drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in_layer

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Jan 16, 2025 at 02:17:26PM +0800, Frank.C wrote:
> From: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
> 
> [ Upstream commit ac2140449184a26eac99585b7f69814bd3ba8f2d ]
> 
> This commit addresses a potential null pointer dereference issue in the
> `dcn32_acquire_idle_pipe_for_head_pipe_in_layer` function. The issue
> could occur when `head_pipe` is null.
> 
> The fix adds a check to ensure `head_pipe` is not null before asserting
> it. If `head_pipe` is null, the function returns NULL to prevent a
> potential null pointer dereference.
> 
> Reported by smatch:
> drivers/gpu/drm/amd/amdgpu/../display/dc/resource/dcn32/dcn32_resource.c:2690 dcn32_acquire_idle_pipe_for_head_pipe_in_layer() error: we previously assumed 'head_pipe' could be null (see line 2681)
> 
> Cc: Tom Chung <chiahsuan.chung@amd.com>
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> Cc: Roman Li <roman.li@amd.com>
> Cc: Alex Hung <alex.hung@amd.com>
> Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Hamza Mahfooz <hamza.mahfooz@amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
> Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> Signed-off-by: Frank.C <tom.and.jerry.official.mail@gmail.com>

I need a real name here, sorry.

greg k-h