Reporting a slab-use-after-free in amdgpu

[Joonkyo Jung]

Hi Vitaly,

No worries, thank you for working on the patches!

I have also confirmed that with the inflight patch, issue No.1
(use-after-free) seems to be resolved.
However, I have reproduced issue No.3 (slab-use-after-free) even with the
patch for issue No.1 applied - if it's the first program tested after
reboot.
(i.e., if any other bugs are tested before the slab-use-after-free, it does
not reproduce).

Could you check if the bug reproduces in this condition for you too?
I will check and see why this is happening and update you if I have
something new.

Thank you!

Best,
Joonkyo



On Fri, Mar 8, 2024 at 12:45 PM vitaly prosyak <vprosyak at amd.com> wrote:

> Hi Joonkyo,
> Sorry for the delay.
> Yes, sure, I reproduced issue 2 (null-ptr-deref in amdgpu) and I will
> provide the fix soon.
> However, issue No. 3 is no longer reproducible if the recent patch
> inflight is applied which fixes issue No 1.
>
> Do you see the same behavior?
>
> Thanks in advance, Vitaly
> On 2024-03-07 20:18, Joonkyo Jung wrote:
>
> Hello,
> thank you for patching the first bug we have sent!
>
> Just a quick touch base with you, to ask if there has been any update on
> our other two bugs.
> They were each sent with emails titled
> "Reporting a slab-use-after-free in amdgpu" (this one)
> "Reporting a null-ptr-deref in amdgpu".
>
> Thank you!
>
> Best,
> Joonkyo
>
>
> 2024년 2월 16일 (금) 오후 6:22, Joonkyo Jung <joonkyoj at yonsei.ac.kr>님이 작성:
>
>> Hello,
>>
>> We would like to report a slab-use-after-free bug in the AMDGPU DRM
>> driver in the linux kernel v6.8-rc4 that we found with our customized
>> Syzkaller.
>> The bug can be triggered by sending two ioctls to the AMDGPU DRM driver
>> in succession.
>>
>> In amdgpu_bo_move, struct ttm_resource *old_mem = bo->resource is
>> assigned.
>> As you can see on the alloc & free stack calls, on the same function
>> amdgpu_bo_move,
>> amdgpu_move_blit in the end frees bo->resource at
>> ttm_bo_move_accel_cleanup with ttm_bo_wait_free_node(bo, man->use_tt).
>> But amdgpu_bo_move continues after that, reaching
>> trace_amdgpu_bo_move(abo, new_mem->mem_type, old_mem->mem_type) at the end,
>> causing the use-after-free bug.
>>
>> Steps to reproduce are as below.
>> union drm_amdgpu_gem_create *arg1;
>>
>> arg1 = malloc(sizeof(union drm_amdgpu_gem_create));
>> arg1->in.bo_size = 0x8;
>> arg1->in.alignment = 0x0;
>> arg1->in.domains = 0x4;
>> arg1->in.domain_flags = 0x9;
>> ioctl(fd, 0xc0206440, arg1);
>>
>> arg1->in.bo_size = 0x7fffffff;
>> arg1->in.alignment = 0x0;
>> arg1->in.domains = 0x4;
>> arg1->in.domain_flags = 0x9;
>> ioctl(fd, 0xc0206440, arg1);
>>
>> The KASAN report is as follows:
>> ==================================================================
>> BUG: KASAN: slab-use-after-free in amdgpu_bo_move+0x1479/0x1550
>> Read of size 4 at addr ffff88800f5bee80 by task syz-executor/219
>> Call Trace:
>>  <TASK>
>>  amdgpu_bo_move+0x1479/0x1550
>>  ttm_bo_handle_move_mem+0x4d0/0x700
>>  ttm_mem_evict_first+0x945/0x1230
>>  ttm_bo_mem_space+0x6c7/0x940
>>  ttm_bo_validate+0x286/0x650
>>  ttm_bo_init_reserved+0x34c/0x490
>>  amdgpu_bo_create+0x94b/0x1610
>>  amdgpu_bo_create_user+0xa3/0x130
>>  amdgpu_gem_create_ioctl+0x4bc/0xc10
>>  drm_ioctl_kernel+0x300/0x410
>>  drm_ioctl+0x648/0xb30
>>  amdgpu_drm_ioctl+0xc8/0x160
>>  </TASK>
>>
>> Allocated by task 219:
>>  kmalloc_trace+0x211/0x390
>>  amdgpu_vram_mgr_new+0x1d6/0xbe0
>>  ttm_resource_alloc+0xfd/0x1e0
>>  ttm_bo_mem_space+0x255/0x940
>>  ttm_bo_validate+0x286/0x650
>>  ttm_bo_init_reserved+0x34c/0x490
>>  amdgpu_bo_create+0x94b/0x1610
>>  amdgpu_bo_create_user+0xa3/0x130
>>  amdgpu_gem_create_ioctl+0x4bc/0xc10
>>  drm_ioctl_kernel+0x300/0x410
>>  drm_ioctl+0x648/0xb30
>>  amdgpu_drm_ioctl+0xc8/0x160
>>
>> Freed by task 219:
>>  kfree+0x111/0x2d0
>>  ttm_resource_free+0x17e/0x1e0
>>  ttm_bo_move_accel_cleanup+0x77e/0x9b0
>>  amdgpu_move_blit+0x3db/0x670
>>  amdgpu_bo_move+0xfa2/0x1550
>>  ttm_bo_handle_move_mem+0x4d0/0x700
>>  ttm_mem_evict_first+0x945/0x1230
>>  ttm_bo_mem_space+0x6c7/0x940
>>  ttm_bo_validate+0x286/0x650
>>  ttm_bo_init_reserved+0x34c/0x490
>>  amdgpu_bo_create+0x94b/0x1610
>>  amdgpu_bo_create_user+0xa3/0x130
>>  amdgpu_gem_create_ioctl+0x4bc/0xc10
>>  drm_ioctl_kernel+0x300/0x410
>>  drm_ioctl+0x648/0xb30
>>  amdgpu_drm_ioctl+0xc8/0x160
>>
>> The buggy address belongs to the object at ffff88800f5bee70
>>  which belongs to the cache kmalloc-96 of size 96
>> The buggy address is located 16 bytes inside of
>>  freed 96-byte region [ffff88800f5bee70, ffff88800f5beed0)
>>
>> Should you need any more information, please do not hesitate to contact
>> us.
>>
>> Best regards,
>> Joonkyo Jung
>>
>
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