Re: [PATCH v2] amdgpu/vcn: vcn dec_msg integer overflow fix

On Mon, Aug 10, 2026 at 4:40 PM David (Ming Qiang) Wu <[email protected]> wrote:
>
> if supplied msg[2] in the header is too large around
> 0x40000000, 4 times of this unsigned 32 bit value will
> overflow and the test could pass.
>
> v2: using kernel helpers to check the overflow.
>     this needs 2 checks: multiplication and addition
>
> Signed-off-by: David (Ming Qiang) Wu <[email protected]>

Reviewed-by: Alex Deucher <[email protected]>

> ---
>  drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c | 6 ++++--
>  drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c | 6 ++++--
>  2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c
> index 81bba3ec2a93..7a301cfe91ee 100644
> --- a/drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v3_0.c
> @@ -1910,7 +1910,7 @@ static int vcn_v3_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
>         struct ttm_operation_ctx ctx = { false, false };
>         struct amdgpu_device *adev = p->adev;
>         struct amdgpu_bo_va_mapping *map;
> -       uint32_t *msg, num_buffers, len_dw;
> +       uint32_t *msg, num_buffers, len_dw, mul, total;
>         struct amdgpu_bo *bo;
>         uint64_t start, end;
>         unsigned int i;
> @@ -1965,7 +1965,9 @@ static int vcn_v3_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
>         num_buffers = msg[2];
>
>         /* Verify that all indices fit within the claimed length. Each index is 4 DWORDs */
> -       if (num_buffers > len_dw || 6 + num_buffers * 4 > len_dw) {
> +       if (check_mul_overflow(num_buffers, 4u, &mul) ||
> +           check_add_overflow(6u, mul, &total) ||
> +           total > len_dw) {
>                 DRM_ERROR("VCN message has too many buffers!\n");
>                 r = -EINVAL;
>                 goto out;
> diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c
> index 0cce78b205a8..413854fcf84a 100644
> --- a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c
> @@ -1826,7 +1826,7 @@ static int vcn_v4_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
>         struct ttm_operation_ctx ctx = { false, false };
>         struct amdgpu_device *adev = p->adev;
>         struct amdgpu_bo_va_mapping *map;
> -       uint32_t *msg, num_buffers, len_dw;
> +       uint32_t *msg, num_buffers, len_dw, mul, total;
>         struct amdgpu_bo *bo;
>         uint64_t start, end;
>         unsigned int i;
> @@ -1881,7 +1881,9 @@ static int vcn_v4_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
>         num_buffers = msg[2];
>
>         /* Verify that all indices fit within the claimed length. Each index is 4 DWORDs */
> -       if (num_buffers > len_dw || 6 + num_buffers * 4 > len_dw) {
> +       if (check_mul_overflow(num_buffers, 4u, &mul) ||
> +           check_add_overflow(6u, mul, &total) ||
> +           total > len_dw) {
>                 DRM_ERROR("VCN message has too many buffers!\n");
>                 r = -EINVAL;
>                 goto out;
> --
> 2.43.0
>