drm/amdgpu: Fix race condition in amdgpu_mn_unregister

Exchange locking order of adev->mn_lock and mm_sem, so that
rmn->mm->mmap_sem can be taken safely, protected by adev->mn_lock,
when amdgpu_mn_destroy runs concurrently.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
index 1b2105c..d12dff9 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
@@ -71,12 +71,11 @@ static void amdgpu_mn_destroy(struct work_struct *work)
        struct amdgpu_mn_node *node, *next_node;
        struct amdgpu_bo *bo, *next_bo;
 
-       down_write(&rmn->mm->mmap_sem);
        mutex_lock(&adev->mn_lock);
+       down_write(&rmn->mm->mmap_sem);
        hash_del(&rmn->node);
        rbtree_postorder_for_each_entry_safe(node, next_node, &rmn->objects,
                                             it.rb) {
-
                interval_tree_remove(&node->it, &rmn->objects);
                list_for_each_entry_safe(bo, next_bo, &node->bos, mn_list) {
                        bo->mn = NULL;
@@ -84,8 +83,8 @@ static void amdgpu_mn_destroy(struct work_struct *work)
                }
                kfree(node);
        }
-       mutex_unlock(&adev->mn_lock);
        up_write(&rmn->mm->mmap_sem);
+       mutex_unlock(&adev->mn_lock);
        mmu_notifier_unregister_no_release(&rmn->mn, rmn->mm);
        kfree(rmn);
 }
@@ -182,8 +181,8 @@ static struct amdgpu_mn *amdgpu_mn_get(struct amdgpu_device *adev)
        struct amdgpu_mn *rmn;
        int r;
 
-       down_write(&mm->mmap_sem);
        mutex_lock(&adev->mn_lock);
+       down_write(&mm->mmap_sem);
 
        hash_for_each_possible(adev->mn_hash, rmn, node, (unsigned long)mm)
                if (rmn->mm == mm)
@@ -207,14 +206,14 @@ static struct amdgpu_mn *amdgpu_mn_get(struct amdgpu_device *adev)
        hash_add(adev->mn_hash, &rmn->node, (unsigned long)mm);
 
 release_locks:
-       mutex_unlock(&adev->mn_lock);
        up_write(&mm->mmap_sem);
+       mutex_unlock(&adev->mn_lock);
 
        return rmn;
 
 free_rmn:
-       mutex_unlock(&adev->mn_lock);
        up_write(&mm->mmap_sem);
+       mutex_unlock(&adev->mn_lock);
        kfree(rmn);
 
        return ERR_PTR(r);
@@ -288,14 +287,18 @@ int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr)
 void amdgpu_mn_unregister(struct amdgpu_bo *bo)
 {
        struct amdgpu_device *adev = bo->adev;
-       struct amdgpu_mn *rmn = bo->mn;
+       struct amdgpu_mn *rmn;
        struct list_head *head;
 
-       if (rmn == NULL)
+       mutex_lock(&adev->mn_lock);
+
+       rmn = bo->mn;
+       if (rmn == NULL) {
+               mutex_unlock(&adev->mn_lock);
                return;
+       }
 
        down_write(&rmn->mm->mmap_sem);
-       mutex_lock(&adev->mn_lock);
 
        /* save the next list entry for later */
        head = bo->mn_list.next;
@@ -310,6 +313,6 @@ void amdgpu_mn_unregister(struct amdgpu_bo *bo)
                kfree(node);
        }
 
-       mutex_unlock(&adev->mn_lock);
        up_write(&rmn->mm->mmap_sem);
+       mutex_unlock(&adev->mn_lock);
 }