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

[Leo Liu]

On 06/25/2018 04:42 PM, Alex Deucher wrote:
> On Mon, Jun 25, 2018 at 4:37 PM, James Zhu <jamesz at amd.com> wrote:
>>
>> On 2018-06-25 04:32 PM, Alex Deucher wrote:
>>> On Mon, Jun 25, 2018 at 4:26 PM, James Zhu <jamesz at amd.com> wrote:
>>>>
>>>> On 2018-06-25 04:02 PM, Alex Deucher wrote:
>>>>> 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
>>>> Need add UVD_ENC also:
>>>>         if ( ring->funcs->type != AMDGPU_RING_TYPE_UVD &&
>>>>               ring->funcs->type != AMDGPU_RING_TYPE_UVD_ENC ) {
>>>>
>>> The old code never checked against the enc rings.  Are you sure they
>>> have the same limitation?
>> I am wrong. thanks! James
> Actually does the uvd decode ring still have this limitation or is
> this just some leftover from a hw limitation on an older asic?
The code here inherited from old ASICs, and not be revisited since there 
is no problem in functional wise.


>   If
> it's still required, the current code in
> amdgpu_fence_driver_start_ring() won't work for multiple instances.
> The fences for the rings will overwrite each other.
IIRC Vega20 with 2 instances have separated runtime environment, that 
should have fence separated as well.

Regards,
Leo



>
> Alex
>
>>> Alex
>>>
>>>> After this, this patch is Reviewed-by: James Zhu <James.Zhu at amd.com>
>>>>
>>>> James
>>>>
>>>>>>                    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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>>>>>> amd-gfx at lists.freedesktop.org
>>>>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>>>>> _______________________________________________
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>>>>> amd-gfx at lists.freedesktop.org
>>>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>>>>