Am 13.06.20 um 14:28 schrieb Xiyu Yang:

ttm_bo_vm_fault_reserved() invokes dma_fence_get(), which returns a reference of the specified dma_fence object to "moving" with increased refcnt.

When ttm_bo_vm_fault_reserved() returns, local variable "moving" becomes invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in several exception handling paths of ttm_bo_vm_fault_reserved(). When those error scenarios occur such as "err" equals to -EBUSY, the function forgets to decrease the refcnt increased by dma_fence_get(), causing a refcnt leak.

Fix this issue by calling dma_fence_put() when no_wait_gpu flag is equals to true.

Signed-off-by: Xiyu Yang xiyuyang19@fudan.edu.cn Signed-off-by: Xin Tan tanxin.ctf@gmail.com

Good catch, Reviewed-by: Christian König christian.koenig@amd.com.

Going to pick that up for drm-misc-fixes.

Christian.

---

drivers/gpu/drm/ttm/ttm_bo_vm.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c index a43aa7275f12..fa03fab02076 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c @@ -300,8 +300,10 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf, break; case -EBUSY: case -ERESTARTSYS:

• 	dma_fence_put(moving);
  return VM_FAULT_NOPAGE;
  

  default:

• 	dma_fence_put(moving);
  return VM_FAULT_SIGBUS;
  

  }