[PATCH v3] drm/amd/display: Prevent potential buffer overflow in map_hw_resources

[Srinivasan Shanmugam]

Adds a check in the map_hw_resources function to prevent a potential
buffer overflow. The function was accessing arrays using an index that
could potentially be greater than the size of the arrays, leading to a
buffer overflow.

Adds a check to ensure that the index is within the bounds of the
arrays. If the index is out of bounds, an error message is printed and
break it will continue execution with just ignoring extra data early to
prevent the buffer overflow.

Reported by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/dml2_wrapper.c:79 map_hw_resources() error: buffer overflow 'dml2->v20.scratch.dml_to_dc_pipe_mapping.disp_cfg_to_stream_id' 6 <= 7
drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/dml2_wrapper.c:81 map_hw_resources() error: buffer overflow 'dml2->v20.scratch.dml_to_dc_pipe_mapping.disp_cfg_to_plane_id' 6 <= 7

Fixes: 482ce89eec1b ("drm/amd/display: Introduce DML2")
Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
Cc: Roman Li <roman.li at amd.com>
Cc: Qingqing Zhuo <Qingqing.Zhuo at amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
Cc: Tom Chung <chiahsuan.chung at amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
---
v3:
 - s/return/break as return may leave the system in a bad state

 drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c b/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c
index 26307e599614..2a58a7687bdb 100644
--- a/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c
+++ b/drivers/gpu/drm/amd/display/dc/dml2/dml2_wrapper.c
@@ -76,6 +76,11 @@ static void map_hw_resources(struct dml2_context *dml2,
 			in_out_display_cfg->hw.DLGRefClkFreqMHz = 50;
 		}
 		for (j = 0; j < mode_support_info->DPPPerSurface[i]; j++) {
+			if (i >= __DML2_WRAPPER_MAX_STREAMS_PLANES__) {
+				dml_print("DML::%s: Index out of bounds: i=%d, __DML2_WRAPPER_MAX_STREAMS_PLANES__=%d\n",
+					  __func__, i, __DML2_WRAPPER_MAX_STREAMS_PLANES__);
+				break;
+			}
 			dml2->v20.scratch.dml_to_dc_pipe_mapping.dml_pipe_idx_to_stream_id[num_pipes] = dml2->v20.scratch.dml_to_dc_pipe_mapping.disp_cfg_to_stream_id[i];
 			dml2->v20.scratch.dml_to_dc_pipe_mapping.dml_pipe_idx_to_stream_id_valid[num_pipes] = true;
 			dml2->v20.scratch.dml_to_dc_pipe_mapping.dml_pipe_idx_to_plane_id[num_pipes] = dml2->v20.scratch.dml_to_dc_pipe_mapping.disp_cfg_to_plane_id[i];
-- 
2.34.1