Reporting a slab-use-after-free in amdgpu

[vitaly prosyak]

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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