drm/ttm: ttm object security fixes for render nodes

When a client looks up a ttm object, don't look it up through the device hash
table, but rather from the file hash table. That makes sure that the client
has indeed put a reference on the object, or in gem terms, has opened
the object; either using prime or using the global "name".

To avoid a performance loss, make sure the file hash table entries can be
looked up from under an RCU lock, and as a consequence, replace the rwlock
with a spinlock, since we never need to take it in read mode only anymore.

Finally add a ttm object lookup function for the device hash table, that is
intended to be used when we put a ref object on a base object or, in  gem terms,
when we open the object.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

1 files changed, 54 insertions, 36 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_object.c b/drivers/gpu/drm/ttm/ttm_object.c
index 6fe7b92a82d1..37079859afc8 100644
--- a/drivers/gpu/drm/ttm/ttm_object.c
+++ b/drivers/gpu/drm/ttm/ttm_object.c
@@ -68,7 +68,7 @@
 
 struct ttm_object_file {
         struct ttm_object_device *tdev;
-        rwlock_t lock;
+        spinlock_t lock;
         struct list_head ref_list;
         struct drm_open_hash ref_hash[TTM_REF_NUM];
         struct kref refcount;
@@ -118,6 +118,7 @@ struct ttm_object_device {
  */
 
 struct ttm_ref_object {
+        struct rcu_head rcu_head;
         struct drm_hash_item hash;
         struct list_head head;
         struct kref kref;
@@ -210,10 +211,9 @@ static void ttm_release_base(struct kref *kref)
          * call_rcu() or ttm_base_object_kfree().
          */
 
-        if (base->refcount_release) {
-                ttm_object_file_unref(&base->tfile);
+        ttm_object_file_unref(&base->tfile);
+        if (base->refcount_release)
                 base->refcount_release(&base);
-        }
 }
 
 void ttm_base_object_unref(struct ttm_base_object **p_base)
@@ -229,32 +229,46 @@ EXPORT_SYMBOL(ttm_base_object_unref);
 struct ttm_base_object *ttm_base_object_lookup(struct ttm_object_file *tfile,
                                                uint32_t key)
 {
-        struct ttm_object_device *tdev = tfile->tdev;
-        struct ttm_base_object *uninitialized_var(base);
+        struct ttm_base_object *base = NULL;
         struct drm_hash_item *hash;
+        struct drm_open_hash *ht = &tfile->ref_hash[TTM_REF_USAGE];
         int ret;
 
         rcu_read_lock();
-        ret = drm_ht_find_item_rcu(&tdev->object_hash, key, &hash);
+        ret = drm_ht_find_item_rcu(ht, key, &hash);
 
         if (likely(ret == 0)) {
-                base = drm_hash_entry(hash, struct ttm_base_object, hash);
-                ret = kref_get_unless_zero(&base->refcount) ? 0 : -EINVAL;
+                base = drm_hash_entry(hash, struct ttm_ref_object, hash)->obj;
+                if (!kref_get_unless_zero(&base->refcount))
+                        base = NULL;
         }
         rcu_read_unlock();
 
-        if (unlikely(ret != 0))
-                return NULL;
+        return base;
+}
+EXPORT_SYMBOL(ttm_base_object_lookup);
 
-        if (tfile != base->tfile && !base->shareable) {
-                pr_err("Attempted access of non-shareable object\n");
-                ttm_base_object_unref(&base);
-                return NULL;
+struct ttm_base_object *
+ttm_base_object_lookup_for_ref(struct ttm_object_device *tdev, uint32_t key)
+{
+        struct ttm_base_object *base = NULL;
+        struct drm_hash_item *hash;
+        struct drm_open_hash *ht = &tdev->object_hash;
+        int ret;
+
+        rcu_read_lock();
+        ret = drm_ht_find_item_rcu(ht, key, &hash);
+
+        if (likely(ret == 0)) {
+                base = drm_hash_entry(hash, struct ttm_base_object, hash);
+                if (!kref_get_unless_zero(&base->refcount))
+                        base = NULL;
         }
+        rcu_read_unlock();
 
         return base;
 }
-EXPORT_SYMBOL(ttm_base_object_lookup);
+EXPORT_SYMBOL(ttm_base_object_lookup_for_ref);
 
 int ttm_ref_object_add(struct ttm_object_file *tfile,
                        struct ttm_base_object *base,
@@ -266,21 +280,25 @@ int ttm_ref_object_add(struct ttm_object_file *tfile,
         struct ttm_mem_global *mem_glob = tfile->tdev->mem_glob;
         int ret = -EINVAL;
 
+        if (base->tfile != tfile && !base->shareable)
+                return -EPERM;
+
         if (existed != NULL)
                 *existed = true;
 
         while (ret == -EINVAL) {
-                read_lock(&tfile->lock);
-                ret = drm_ht_find_item(ht, base->hash.key, &hash);
+                rcu_read_lock();
+                ret = drm_ht_find_item_rcu(ht, base->hash.key, &hash);
 
                 if (ret == 0) {
                         ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
-                        kref_get(&ref->kref);
-                        read_unlock(&tfile->lock);
-                        break;
+                        if (!kref_get_unless_zero(&ref->kref)) {
+                                rcu_read_unlock();
+                                break;
+                        }
                 }
 
-                read_unlock(&tfile->lock);
+                rcu_read_unlock();
                 ret = ttm_mem_global_alloc(mem_glob, sizeof(*ref),
                                            false, false);
                 if (unlikely(ret != 0))
@@ -297,19 +315,19 @@ int ttm_ref_object_add(struct ttm_object_file *tfile,
                 ref->ref_type = ref_type;
                 kref_init(&ref->kref);
 
-                write_lock(&tfile->lock);
-                ret = drm_ht_insert_item(ht, &ref->hash);
+                spin_lock(&tfile->lock);
+                ret = drm_ht_insert_item_rcu(ht, &ref->hash);
 
                 if (likely(ret == 0)) {
                         list_add_tail(&ref->head, &tfile->ref_list);
                         kref_get(&base->refcount);
-                        write_unlock(&tfile->lock);
+                        spin_unlock(&tfile->lock);
                         if (existed != NULL)
                                 *existed = false;
                         break;
                 }
 
-                write_unlock(&tfile->lock);
+                spin_unlock(&tfile->lock);
                 BUG_ON(ret != -EINVAL);
 
                 ttm_mem_global_free(mem_glob, sizeof(*ref));
@@ -330,17 +348,17 @@ static void ttm_ref_object_release(struct kref *kref)
         struct ttm_mem_global *mem_glob = tfile->tdev->mem_glob;
 
         ht = &tfile->ref_hash[ref->ref_type];
-        (void)drm_ht_remove_item(ht, &ref->hash);
+        (void)drm_ht_remove_item_rcu(ht, &ref->hash);
         list_del(&ref->head);
-        write_unlock(&tfile->lock);
+        spin_unlock(&tfile->lock);
 
         if (ref->ref_type != TTM_REF_USAGE && base->ref_obj_release)
                 base->ref_obj_release(base, ref->ref_type);
 
         ttm_base_object_unref(&ref->obj);
         ttm_mem_global_free(mem_glob, sizeof(*ref));
-        kfree(ref);
-        write_lock(&tfile->lock);
+        kfree_rcu(ref, rcu_head);
+        spin_lock(&tfile->lock);
 }
 
 int ttm_ref_object_base_unref(struct ttm_object_file *tfile,
@@ -351,15 +369,15 @@ int ttm_ref_object_base_unref(struct ttm_object_file *tfile,
         struct drm_hash_item *hash;
         int ret;
 
-        write_lock(&tfile->lock);
+        spin_lock(&tfile->lock);
         ret = drm_ht_find_item(ht, key, &hash);
         if (unlikely(ret != 0)) {
-                write_unlock(&tfile->lock);
+                spin_unlock(&tfile->lock);
                 return -EINVAL;
         }
         ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
         kref_put(&ref->kref, ttm_ref_object_release);
-        write_unlock(&tfile->lock);
+        spin_unlock(&tfile->lock);
         return 0;
 }
 EXPORT_SYMBOL(ttm_ref_object_base_unref);
@@ -372,7 +390,7 @@ void ttm_object_file_release(struct ttm_object_file **p_tfile)
         struct ttm_object_file *tfile = *p_tfile;
 
         *p_tfile = NULL;
-        write_lock(&tfile->lock);
+        spin_lock(&tfile->lock);
 
         /*
          * Since we release the lock within the loop, we have to
@@ -388,7 +406,7 @@ void ttm_object_file_release(struct ttm_object_file **p_tfile)
         for (i = 0; i < TTM_REF_NUM; ++i)
                 drm_ht_remove(&tfile->ref_hash[i]);
 
-        write_unlock(&tfile->lock);
+        spin_unlock(&tfile->lock);
         ttm_object_file_unref(&tfile);
 }
 EXPORT_SYMBOL(ttm_object_file_release);
@@ -404,7 +422,7 @@ struct ttm_object_file *ttm_object_file_init(struct ttm_object_device *tdev,
         if (unlikely(tfile == NULL))
                 return NULL;
 
-        rwlock_init(&tfile->lock);
+        spin_lock_init(&tfile->lock);
         tfile->tdev = tdev;
         kref_init(&tfile->refcount);
         INIT_LIST_HEAD(&tfile->ref_list);