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Message-ID: <2a4448cb-ac01-71fc-9335-68acdded0a78@amd.com>
Date: Mon, 21 Aug 2023 11:31:30 +0200
From: Christian König <christian.koenig@....com>
To: Su Hui <suhui@...china.com>, alexander.deucher@....com,
Xinhui.Pan@....com, airlied@...il.com, daniel@...ll.ch
Cc: Hawking.Zhang@....com, le.ma@....com, lijo.lazar@....com,
yifan1.zhang@....com, candice.li@....com, guchun.chen@....com,
Yuliang.Shi@....com, amd-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
kernel-janitors@...r.kernel.org, christophe.jaillet@...adoo.fr
Subject: Re: [PATCH v2] drm/amdgpu: Avoid possible buffer overflow
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@...china.com>
> ---
> 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.
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 ||
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