[PATCH] drm/amdgpu: fix NULL pointer dereference when run App with DRI_PRIME=1

[Christian König]

Am 25.05.2018 um 09:20 schrieb Zhang, Jerry (Junwei):
> On 05/25/2018 02:44 PM, Christian König wrote:
>> NAK, that probably just fixed the symptom but not the underlying 
>> problem.
>>
>> Somebody is accessing the page array when it should never be accessed.
>
> If prime import as GTT bo by default(now it's CPU bo), it would 
> happens quickly when GTT sg bo creation rather than next cs validation.
>
> Since ttm_sg_tt_init() only allocates gtt->ttm.dma_address if sg bo is 
> created, it would fail to access ttm->pages when ttm populate.

And exactly that's the problem, and imported BO should never populate.

>
> current error happens in ttm populate from cs validation, the sg bo is 
> imported from exporter.
>
>>
>> How did you manage to trigger this?
>
> PRI_PRIME=1 with Unigine heaven.

Going to give that a try, but the last time I check that worked as expected.

Thanks,
Christian.

>
> Regards,
> Jerry
>
>>
>> Regards,
>> Christian.
>>
>> Am 25.05.2018 um 07:41 schrieb Junwei Zhang:
>>> [  632.679861] BUG: unable to handle kernel NULL pointer dereference 
>>> at (null)
>>> [  632.679892] IP: drm_prime_sg_to_page_addr_arrays+0x52/0xb0 [drm]
>>> <snip>
>>> [  632.680011] Call Trace:
>>> [  632.680082]  amdgpu_ttm_tt_populate+0x3e/0xa0 [amdgpu]
>>> [  632.680092]  ttm_tt_populate.part.7+0x22/0x60 [amdttm]
>>> [  632.680098]  amdttm_tt_bind+0x52/0x60 [amdttm]
>>> [  632.680106]  ttm_bo_handle_move_mem+0x54b/0x5c0 [amdttm]
>>> [  632.680112]  ? find_next_bit+0xb/0x10
>>> [  632.680119]  amdttm_bo_validate+0x11d/0x130 [amdttm]
>>> [  632.680176]  amdgpu_cs_bo_validate+0x9d/0x150 [amdgpu]
>>> [  632.680232]  amdgpu_cs_validate+0x41/0x270 [amdgpu]
>>> [  632.680288]  amdgpu_cs_list_validate+0xc7/0x1a0 [amdgpu]
>>> [  632.680343]  amdgpu_cs_ioctl+0x1634/0x1c00 [amdgpu]
>>> [  632.680401]  ? amdgpu_cs_find_mapping+0x120/0x120 [amdgpu]
>>> [  632.680416]  drm_ioctl_kernel+0x6b/0xb0 [drm]
>>> [  632.680431]  drm_ioctl+0x3e4/0x450 [drm]
>>> [  632.680485]  ? amdgpu_cs_find_mapping+0x120/0x120 [amdgpu]
>>> [  632.680537]  amdgpu_drm_ioctl+0x4c/0x80 [amdgpu]
>>> [  632.680542]  do_vfs_ioctl+0xa4/0x600
>>> [  632.680546]  ? SyS_futex+0x7f/0x180
>>> [  632.680549]  SyS_ioctl+0x79/0x90
>>> [  632.680554]  entry_SYSCALL_64_fastpath+0x24/0xab
>>>
>>> Signed-off-by: Junwei Zhang <Jerry.Zhang at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>> index 57d4da6..b293809 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>> @@ -1212,7 +1212,7 @@ static struct ttm_tt *amdgpu_ttm_tt_create(struct
>>> ttm_buffer_object *bo,
>>>       gtt->ttm.ttm.func = &amdgpu_backend_func;
>>>       /* allocate space for the uninitialized page entries */
>>> -    if (ttm_sg_tt_init(&gtt->ttm, bo, page_flags)) {
>>> +    if (ttm_dma_tt_init(&gtt->ttm, bo, page_flags)) {
>>>           kfree(gtt);
>>>           return NULL;
>>>       }
>>