[PATCH] drm/amd/display: guard NULL secondary pipe in dcn_validate_bandwidth()

[Dmitriy Chumachenko]

resource_find_free_secondary_pipe_legacy() returns NULL when no free
pipe is available, but the result is only passed to ASSERT() (a
WARN_ON_ONCE() that does not stop execution) and then dereferenced in
split_stream_across_pipes() and dcn_bw_calc_rq_dlg_ttu().

The sibling resource callers (dcn10/dcn20/dcn201) already NULL-check
this function's result. Do the same here and skip the split when no
free pipe is available.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 74c49c7ac14f ("drm/amdgpu/display: Add calcs code for DCN")
Signed-off-by: Dmitriy Chumachenko <Dmitry.Chumachenko@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/amd/display/dc/dml/calcs/dcn_calcs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dml/calcs/dcn_calcs.c b/drivers/gpu/drm/amd/display/dc/dml/calcs/dcn_calcs.c
index 61553e24d53e..de54807ade43 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/calcs/dcn_calcs.c
+++ b/drivers/gpu/drm/amd/display/dc/dml/calcs/dcn_calcs.c
@@ -1261,10 +1261,12 @@ bool dcn_validate_bandwidth(
 						/* pipe not split previously needs split */
 						hsplit_pipe = resource_find_free_secondary_pipe_legacy(&context->res_ctx, pool, pipe);
 						ASSERT(hsplit_pipe);
-						split_stream_across_pipes(&context->res_ctx, pool, pipe, hsplit_pipe);
+						if (hsplit_pipe)
+							split_stream_across_pipes(&context->res_ctx, pool, pipe, hsplit_pipe);
 					}
 
-					dcn_bw_calc_rq_dlg_ttu(dc, v, hsplit_pipe, input_idx);
+					if (hsplit_pipe)
+						dcn_bw_calc_rq_dlg_ttu(dc, v, hsplit_pipe, input_idx);
 				} else if (hsplit_pipe && hsplit_pipe->plane_state == pipe->plane_state) {
 					/* merge previously split pipe */
 					pipe->bottom_pipe = hsplit_pipe->bottom_pipe;
-- 
2.49.0