[bug report] drm/amdgpu: Auto-validate DMABuf imports in compute VMs

[Dan Carpenter]

Hello Felix Kuehling,

This is a semi-automatic email about new static checker warnings.

    drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:1480 amdgpu_vm_handle_moved()
    warn: variable dereferenced before check 'bo_va->base.bo' (see line 1453)

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
  1452						 base.vm_status);
  1453			resv = bo_va->base.bo->tbo.base.resv;
                               ^^^^^^^^^^^^^^^^
Unchecked dereference

  1454			spin_unlock(&vm->status_lock);
  1455	
  1456			/* Try to reserve the BO to avoid clearing its ptes */
  1457			if (!adev->debug_vm && dma_resv_trylock(resv)) {
  1458				clear = false;
  1459				unlock = true;
  1460			/* The caller is already holding the reservation lock */
  1461			} else if (ticket && dma_resv_locking_ctx(resv) == ticket) {
  1462				clear = false;
  1463				unlock = false;
  1464			/* Somebody else is using the BO right now */
  1465			} else {
  1466				clear = true;
  1467				unlock = false;
  1468			}
  1469	
  1470			r = amdgpu_vm_bo_update(adev, bo_va, clear);
  1471	
  1472			if (unlock)
  1473				dma_resv_unlock(resv);
  1474			if (r)
  1475				return r;
  1476	
  1477			/* Remember evicted DMABuf imports in compute VMs for later
  1478			 * validation
  1479			 */
  1480			if (vm->is_compute_context && bo_va->base.bo &&
                                                      ^^^^^^^^^^^^^^
The patch adds this NULL check but hopefully it's not required.

  1481			    bo_va->base.bo->tbo.base.import_attach &&
  1482			    (!bo_va->base.bo->tbo.resource ||

regards,
dan carpenter