1 files changed, 28 insertions, 10 deletions

diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c
index 85b5ee4defa4..d8eead5d106d 100644
--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@ -141,7 +141,12 @@ static struct ib_uobject *alloc_uobj(struct ib_ucontext *context,
 	 */
 	uobj->context = context;
 	uobj->type = type;
-	atomic_set(&uobj->usecnt, 0);
+	/*
+	 * Allocated objects start out as write locked to deny any other
+	 * syscalls from accessing them until they are committed. See
+	 * rdma_alloc_commit_uobject
+	 */
+	atomic_set(&uobj->usecnt, -1);
 	kref_init(&uobj->ref);
 
 	return uobj;
@@ -196,7 +201,15 @@ static struct ib_uobject *lookup_get_idr_uobject(const struct uverbs_obj_type *t
 		goto free;
 	}
 
-	uverbs_uobject_get(uobj);
+	/*
+	 * The idr_find is guaranteed to return a pointer to something that
+	 * isn't freed yet, or NULL, as the free after idr_remove goes through
+	 * kfree_rcu(). However the object may still have been released and
+	 * kfree() could be called at any time.
+	 */
+	if (!kref_get_unless_zero(&uobj->ref))
+		uobj = ERR_PTR(-ENOENT);
+
 free:
 	rcu_read_unlock();
 	return uobj;
@@ -399,13 +412,13 @@ static int __must_check remove_commit_fd_uobject(struct ib_uobject *uobj,
 	return ret;
 }
 
-static void lockdep_check(struct ib_uobject *uobj, bool exclusive)
+static void assert_uverbs_usecnt(struct ib_uobject *uobj, bool exclusive)
 {
 #ifdef CONFIG_LOCKDEP
 	if (exclusive)
-		WARN_ON(atomic_read(&uobj->usecnt) > 0);
+		WARN_ON(atomic_read(&uobj->usecnt) != -1);
 	else
-		WARN_ON(atomic_read(&uobj->usecnt) == -1);
+		WARN_ON(atomic_read(&uobj->usecnt) <= 0);
 #endif
 }
 
@@ -444,7 +457,7 @@ int __must_check rdma_remove_commit_uobject(struct ib_uobject *uobj)
 		WARN(true, "ib_uverbs: Cleanup is running while removing an uobject\n");
 		return 0;
 	}
-	lockdep_check(uobj, true);
+	assert_uverbs_usecnt(uobj, true);
 	ret = _rdma_remove_commit_uobject(uobj, RDMA_REMOVE_DESTROY);
 
 	up_read(&ucontext->cleanup_rwsem);
@@ -474,16 +487,17 @@ int rdma_explicit_destroy(struct ib_uobject *uobject)
 		WARN(true, "ib_uverbs: Cleanup is running while removing an uobject\n");
 		return 0;
 	}
-	lockdep_check(uobject, true);
+	assert_uverbs_usecnt(uobject, true);
 	ret = uobject->type->type_class->remove_commit(uobject,
 						       RDMA_REMOVE_DESTROY);
 	if (ret)
-		return ret;
+		goto out;
 
 	uobject->type = &null_obj_type;
 
+out:
 	up_read(&ucontext->cleanup_rwsem);
-	return 0;
+	return ret;
 }
 
 static void alloc_commit_idr_uobject(struct ib_uobject *uobj)
@@ -527,6 +541,10 @@ int rdma_alloc_commit_uobject(struct ib_uobject *uobj)
 		return ret;
 	}
 
+	/* matches atomic_set(-1) in alloc_uobj */
+	assert_uverbs_usecnt(uobj, true);
+	atomic_set(&uobj->usecnt, 0);
+
 	uobj->type->type_class->alloc_commit(uobj);
 	up_read(&uobj->context->cleanup_rwsem);
 
@@ -561,7 +579,7 @@ static void lookup_put_fd_uobject(struct ib_uobject *uobj, bool exclusive)
 
 void rdma_lookup_put_uobject(struct ib_uobject *uobj, bool exclusive)
 {
-	lockdep_check(uobj, exclusive);
+	assert_uverbs_usecnt(uobj, exclusive);
 	uobj->type->type_class->lookup_put(uobj, exclusive);
 	/*
 	 * In order to unlock an object, either decrease its usecnt for