[PATCH] drm/amdgpu: Avoid possible buffer overflow

From: Su Hui
Date: Mon Aug 21 2023 - 02:20:27 EST


smatch error:
drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c:1257 amdgpu_discovery_reg_base_init() error:
testing array offset 'adev->vcn.num_vcn_inst' after use.

change the assignment order to avoid buffer overflow.

Fixes: c40bdfb2ffa4 ("drm/amdgpu: fix incorrect VCN revision in SRIOV")
Signed-off-by: Su Hui <suhui@xxxxxxxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
index 8e1cfc87122d..ba95526c3d45 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
@@ -1250,11 +1250,12 @@ 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);
--
2.30.2