IB/uverbs: Fix unbalanced unlock on error path for rdma_explicit_destroy

If remove_commit fails then the lock is left locked while the uobj still
exists. Eventually the kernel will deadlock.

lockdep detects this and says:

 test/4221 is leaving the kernel with locks still held!
 1 lock held by test/4221:
  #0:  (&ucontext->cleanup_rwsem){.+.+}, at: [<000000001e5c7523>] rdma_explicit_destroy+0x37/0x120 [ib_uverbs]

Fixes: 4da70da2 ("IB/core: Explicitly destroy an object while keeping uobject")
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/rdma_core.c

@@ -491,12 +491,13 @@ int rdma_explicit_destroy(struct ib_uobject *uobject)
 	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)