linux-kernel - [PATCH 6.6 388/638] drm/amdgpu: Fix potential out-of-bounds access in 'amdgpu_discovery_reg_base

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Message-ID: <20240324230116.1348576-389-sashal@kernel.org>
Date: Sun, 24 Mar 2024 18:57:05 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Srinivasan Shanmugam <srinivasan.shanmugam@....com>,
	Christian König <christian.koenig@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.6 388/638] drm/amdgpu: Fix potential out-of-bounds access in 'amdgpu_discovery_reg_base_init()'

From: Srinivasan Shanmugam <srinivasan.shanmugam@....com>

[ Upstream commit cdb637d339572398821204a1142d8d615668f1e9 ]

The issue arises when the array 'adev->vcn.vcn_config' is accessed
before checking if the index 'adev->vcn.num_vcn_inst' is within the
bounds of the array.

The fix involves moving the bounds check before the array access. This
ensures that 'adev->vcn.num_vcn_inst' is within the bounds of the array
before it is used as an index.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c:1289 amdgpu_discovery_reg_base_init() error: testing array offset 'adev->vcn.num_vcn_inst' after use.

Fixes: a0ccc717c4ab ("drm/amdgpu/discovery: validate VCN and SDMA instances")
Cc: Christian König <christian.koenig@....com>
Cc: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@....com>
Reviewed-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
index 68a901287264f..cf2faeae1d0db 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
@@ -1270,11 +1270,10 @@ static int amdgpu_discovery_reg_base_init(struct amdgpu_device *adev)
 				 *     0b10 : encode is disabled
 				 *     0b01 : decode is disabled
 				 */
-				adev->vcn.vcn_config[adev->vcn.num_vcn_inst] =
-					ip->revision & 0xc0;
-				ip->revision &= ~0xc0;
 				if (adev->vcn.num_vcn_inst <
 				    AMDGPU_MAX_VCN_INSTANCES) {
+					adev->vcn.vcn_config[adev->vcn.num_vcn_inst] =
+						ip->revision & 0xc0;
 					adev->vcn.num_vcn_inst++;
 					adev->vcn.inst_mask |=
 						(1U << ip->instance_number);
@@ -1285,6 +1284,7 @@ static int amdgpu_discovery_reg_base_init(struct amdgpu_device *adev)
 						adev->vcn.num_vcn_inst + 1,
 						AMDGPU_MAX_VCN_INSTANCES);
 				}
+				ip->revision &= ~0xc0;
 			}
 			if (le16_to_cpu(ip->hw_id) == SDMA0_HWID ||
 			    le16_to_cpu(ip->hw_id) == SDMA1_HWID ||
-- 
2.43.0