drm/amd/pm: fix the Out-of-bounds read warning

using index i - 1U may beyond element index
for mc_data[] when i = 0.

Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Tim Huang <Tim.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/ppatomctrl.c b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/ppatomctrl.c
index b1b4c09..b56298d 100644 (file)
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/ppatomctrl.c
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/ppatomctrl.c
@@ -73,8 +73,9 @@ static int atomctrl_retrieve_ac_timing(
                                        j++;
                                } else if ((table->mc_reg_address[i].uc_pre_reg_data &
                                                        LOW_NIBBLE_MASK) == DATA_EQU_PREV) {
-                                       table->mc_reg_table_entry[num_ranges].mc_data[i] =
-                                               table->mc_reg_table_entry[num_ranges].mc_data[i-1];
+                                       if (i)
+                                               table->mc_reg_table_entry[num_ranges].mc_data[i] =
+                                                       table->mc_reg_table_entry[num_ranges].mc_data[i-1];
                                }
                        }
                        num_ranges++;