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SubjectRe: [PATCH] gpu: drm: drm_mm: Fix a sleep-in-atomic-context bug in show_leaks()
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Quoting Jia-Ju Bai (2018-09-01 13:20:41)
> The driver may sleep with holding a spinlock.
>
> The function call paths (from bottom to top) in Linux-4.16 are:
>
> [FUNC] kmalloc(GFP_KERNEL)
> drivers/gpu/drm/drm_mm.c, 130:
> kmalloc in show_leaks
> drivers/gpu/drm/drm_mm.c, 913:
> show_leaks in drm_mm_takedown
> drivers/gpu/drm/drm_vma_manager.c, 107:
> drm_mm_takedown in drm_vma_offset_manager_destroy
> drivers/gpu/drm/drm_vma_manager.c, 106:
> _raw_write_lock in drm_vma_offset_manager_destroy
>
> [FUNC] kmalloc(GFP_KERNEL)
> drivers/gpu/drm/drm_mm.c, 130:
> kmalloc in show_leaks
> drivers/gpu/drm/drm_mm.c, 913:
> show_leaks in drm_mm_takedown
> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 71:
> drm_mm_takedown in amdgpu_vram_mgr_fini
> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c, 70:
> spin_lock in amdgpu_vram_mgr_fini
>
> [FUNC] kmalloc(GFP_KERNEL)
> drivers/gpu/drm/drm_mm.c, 130:
> kmalloc in show_leaks
> drivers/gpu/drm/drm_mm.c, 913:
> show_leaks in drm_mm_takedown
> drivers/gpu/drm/ttm/ttm_bo_manager.c, 128:
> drm_mm_takedown in ttm_bo_man_takedown
> drivers/gpu/drm/ttm/ttm_bo_manager.c, 126:
> spin_lock in ttm_bo_man_takedown
>
> To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.

The bug are above, since those spinlocks do not protect the data and
imply use-after-free.
-Chris

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