Reporting a slab-use-after-free in amdgpu

[Joonkyo Jung]

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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