On 2023/8/21 17:31, Christian König wrote:
Am 21.08.23 um 09:37 schrieb Su Hui:
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>
---
changes in v2:
- fix the error about ip->revision (thanks to Christophe JAILLET).
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 8e1cfc87122d..b07bfd106a9b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
@@ -1250,11 +1250,10 @@ 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);
@@ -1265,6 +1264,7 @@ static int
amdgpu_discovery_reg_base_init(struct amdgpu_device *adev)
adev->vcn.num_vcn_inst + 1,
AMDGPU_MAX_VCN_INSTANCES);
}
+ ip->revision &= ~0xc0;
That doesn't looks correct either. The assignment is intentionally
outside of the "if".
See "adev->vcn.vcn_config[adev->vcn.num_vcn_inst] = ip->revision &
0xc0;" is always valid.
Hi,
if "adev->vcn.vcn_config[adev->vcn.num_vcn_inst] = ip->revision & 0xc0;"
is always valid, then
"adev->vcn.num_vcn_inst< AMDGPU_MAX_VCN_INSTANCES " is always true. So
the below judgement has
no sense.
if (adev->vcn.num_vcn_inst <
AMDGPU_MAX_VCN_INSTANCES) {
On the contrary, if we need this judgement, then
"adev->vcn.vcn_config[adev->vcn.num_vcn_inst] = ip->revision & 0xc0;"is not
always valid, because "adev->vcn.num_vcn_inst >=
AMDGPU_MAX_VCN_INSTANCES" can be true, which cause buffer overflow.
So I think this patch has some sense if I don't make some mistakes.
Su Hui
We just avoid incrementing num_vcn_inst when we already have to many.
Regards,
Christian.
}
if (le16_to_cpu(ip->hw_id) == SDMA0_HWID ||
le16_to_cpu(ip->hw_id) == SDMA1_HWID ||
