[PATCH] drm/amdgpu: fix UBSAN: Undefined behaviour for amdgpu_fence.c

[Alex Deucher]

On Mon, Jun 25, 2018 at 3:17 PM, Leo Liu <leo.liu at amd.com> wrote:
> [    3.866656] index 2 is out of range for type 'amdgpu_uvd_inst [2]'
> [    3.866667] CPU: 0 PID: 59 Comm: kworker/0:1 Not tainted 4.16.0-rc7+ #3
> [    3.866677] Hardware name: Gigabyte Technology Co., Ltd. GA-990FXA-UD7/GA-990FXA-UD7, BIOS F9 06/08/2012
> [    3.866693] Workqueue: events work_for_cpu_fn
> [    3.866702] Call Trace:
> [    3.866710]  dump_stack+0x85/0xc5
> [    3.866719]  ubsan_epilogue+0x9/0x40
> [    3.866727]  __ubsan_handle_out_of_bounds+0x89/0x90
> [    3.866737]  ? rcu_read_lock_sched_held+0x58/0x60
> [    3.866746]  ? __kmalloc+0x26c/0x2d0
> [    3.866846]  amdgpu_fence_driver_start_ring+0x259/0x280 [amdgpu]
> [    3.866896]  amdgpu_ring_init+0x12c/0x710 [amdgpu]
> [    3.866906]  ? sprintf+0x42/0x50
> [    3.866956]  amdgpu_gfx_kiq_init_ring+0x1bc/0x3a0 [amdgpu]
> [    3.867009]  gfx_v8_0_sw_init+0x1ad3/0x2360 [amdgpu]
> [    3.867062]  ? smu7_init+0xec/0x160 [amdgpu]
> [    3.867109]  amdgpu_device_init+0x112c/0x1dc0 [amdgpu]
>
> ring->me might be set as 2 with amdgpu_gfx_kiq_init_ring.
>
> Signed-off-by: Leo Liu <leo.liu at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> index 39ec6b8890a1..6067dae1552f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> @@ -375,8 +375,17 @@ int amdgpu_fence_driver_start_ring(struct amdgpu_ring *ring,
>  {
>         struct amdgpu_device *adev = ring->adev;
>         uint64_t index;
> +       bool uvd_ring = false;
> +       int i;
> +
> +       for (i = 0; i < AMDGPU_MAX_UVD_INSTANCES; ++i) {
> +               if (ring == &adev->uvd.inst[i].ring) {
> +                       uvd_ring = true;
> +                       break;
> +               }
> +       }
>
> -       if (ring != &adev->uvd.inst[ring->me].ring) {
> +       if (!uvd_ring) {

I think we can just simplify this to:
if (ring->funcs->type != AMDGPU_RING_TYPE_UVD)

Alex

>                 ring->fence_drv.cpu_addr = &adev->wb.wb[ring->fence_offs];
>                 ring->fence_drv.gpu_addr = adev->wb.gpu_addr + (ring->fence_offs * 4);
>         } else {
> --
> 2.17.1
>
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