[PATCH 8/9] drm/amdgpu: reserve the root PD while freeing PASIDs

[Christian König]

Free the pasid only while the root PD is reserved. This prevents use after
free in the page fault handling.

Signed-off-by: Christian König <christian.koe...@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehl...@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index 3b954b53a450..db13ddd70a8d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2944,18 +2944,26 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct 
amdgpu_vm *vm)
        struct amdgpu_bo_va_mapping *mapping, *tmp;
        bool prt_fini_needed = !!adev->gmc.gmc_funcs->set_prt;
        struct amdgpu_bo *root;
-       int i, r;
+       int i;
 
        amdgpu_amdkfd_gpuvm_destroy_cb(adev, vm);
 
+       root = amdgpu_bo_ref(vm->root.base.bo);
+       amdgpu_bo_reserve(root, true);
        if (vm->pasid) {
                unsigned long flags;
 
                spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
                idr_remove(&adev->vm_manager.pasid_idr, vm->pasid);
                spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
+               vm->pasid = 0;
        }
 
+       amdgpu_vm_free_pts(adev, vm, NULL);
+       amdgpu_bo_unreserve(root);
+       amdgpu_bo_unref(&root);
+       WARN_ON(vm->root.base.bo);
+
        drm_sched_entity_destroy(&vm->direct);
        drm_sched_entity_destroy(&vm->delayed);
 
@@ -2980,16 +2988,6 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct 
amdgpu_vm *vm)
                amdgpu_vm_free_mapping(adev, vm, mapping, NULL);
        }
 
-       root = amdgpu_bo_ref(vm->root.base.bo);
-       r = amdgpu_bo_reserve(root, true);
-       if (r) {
-               dev_err(adev->dev, "Leaking page tables because BO reservation 
failed\n");
-       } else {
-               amdgpu_vm_free_pts(adev, vm, NULL);
-               amdgpu_bo_unreserve(root);
-       }
-       amdgpu_bo_unref(&root);
-       WARN_ON(vm->root.base.bo);
        dma_fence_put(vm->last_update);
        for (i = 0; i < AMDGPU_MAX_VMHUBS; i++)
                amdgpu_vmid_free_reserved(adev, vm, i);
-- 
2.17.1

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