drm/amd/display: Add null check for head_pipe in dcn201_acquire_free_pipe_for_layer

[ Upstream commit f22f4754aaa47d8c59f166ba3042182859e5dff7 ]

This commit addresses a potential null pointer dereference issue in the
`dcn201_acquire_free_pipe_for_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/dcn201/dcn201_resource.c:1016 dcn201_acquire_free_pipe_for_layer() error: we previously assumed 'head_pipe' could be null (see line 1010)

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: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn201/dcn201_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn201/dcn201_resource.c
index 070a4efb308bdf159b22c29ff07f9e839c6779a2..1aeede348bd39b2d014f8660efbda932e6b3bdad 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/resource/dcn201/dcn201_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/resource/dcn201/dcn201_resource.c
@@ -1005,8 +1005,10 @@ static struct pipe_ctx *dcn201_acquire_free_pipe_for_layer(
        struct pipe_ctx *head_pipe = resource_get_otg_master_for_stream(res_ctx, opp_head_pipe->stream);
        struct pipe_ctx *idle_pipe = resource_find_free_secondary_pipe_legacy(res_ctx, pool, head_pipe);
 
-       if (!head_pipe)
+       if (!head_pipe) {
                ASSERT(0);
+               return NULL;
+       }
 
        if (!idle_pipe)
                return NULL;