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    Subject[PATCH 5.14 016/168] drm/amdgpu: fix use after free during BO move
    Date
    From: Christian König <christian.koenig@amd.com>

    commit c92db8d64f9e0313e7ecdc9500db93a5040c9370 upstream.

    The memory backing old_mem is already freed at that point, move the
    check a bit more up.

    Signed-off-by: Christian König <christian.koenig@amd.com>
    Fixes: bfa3357ef9ab ("drm/ttm: allocate resource object instead of embedding it v2")
    Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1699
    Acked-by: Nirmoy Das <nirmoy.das@amd.com>
    Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 18 +++++++++---------
    1 file changed, 9 insertions(+), 9 deletions(-)

    --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
    +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
    @@ -513,6 +513,15 @@ static int amdgpu_bo_move(struct ttm_buf
    goto out;
    }

    + if (bo->type == ttm_bo_type_device &&
    + new_mem->mem_type == TTM_PL_VRAM &&
    + old_mem->mem_type != TTM_PL_VRAM) {
    + /* amdgpu_bo_fault_reserve_notify will re-set this if the CPU
    + * accesses the BO after it's moved.
    + */
    + abo->flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
    + }
    +
    if (adev->mman.buffer_funcs_enabled) {
    if (((old_mem->mem_type == TTM_PL_SYSTEM &&
    new_mem->mem_type == TTM_PL_VRAM) ||
    @@ -543,15 +552,6 @@ static int amdgpu_bo_move(struct ttm_buf
    return r;
    }

    - if (bo->type == ttm_bo_type_device &&
    - new_mem->mem_type == TTM_PL_VRAM &&
    - old_mem->mem_type != TTM_PL_VRAM) {
    - /* amdgpu_bo_fault_reserve_notify will re-set this if the CPU
    - * accesses the BO after it's moved.
    - */
    - abo->flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
    - }
    -
    out:
    /* update statistics */
    atomic64_add(bo->base.size, &adev->num_bytes_moved);

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