[SRU][F][PATCH 1/1] drm/amd/pm: fix the Out-of-bounds read warning

[Bethany Jamison]

From: Jesse Zhang <jesse.zhang at amd.com>

[ Upstream commit 12c6967428a099bbba9dfd247bb4322a984fcc0b ]

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

Signed-off-by: Jesse Zhang <Jesse.Zhang at amd.com>
Reviewed-by: Tim Huang <Tim.Huang at amd.com>
Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
(cherry picked from commit 38e32a0d837443c91c4b615a067b976cfb925376 linux-5.10.y)
CVE-2024-46731
Signed-off-by: Bethany Jamison <bethany.jamison at canonical.com>
---
 drivers/gpu/drm/amd/powerplay/hwmgr/ppatomctrl.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomctrl.c b/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomctrl.c
index 01dc46dc9c8a0..165af862d0542 100644
--- a/drivers/gpu/drm/amd/powerplay/hwmgr/ppatomctrl.c
+++ b/drivers/gpu/drm/amd/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++;
-- 
2.43.0