From d9dc7a3500a58de9bf3861d1a96ffeab42624b4f Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Tue, 13 Feb 2018 12:18:36 +0200 Subject: [PATCH] IB/uverbs: Hold the uobj write lock after allocate This clarifies the design intention that time between allocate and commit has the uobj exclusive to the caller. We already guarantee this by delaying publishing the uobj pointer via idr_insert, fd_install, list_add, etc. Additionally holding the usecnt lock during this period provides extra clarity and more protection against future mistakes. Fixes: 3832125624b7 ("IB/core: Add support for idr types") Signed-off-by: Leon Romanovsky Signed-off-by: Jason Gunthorpe --- drivers/infiniband/core/rdma_core.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c index 85b5ee4defa4..3fe6035abde6 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; @@ -527,6 +532,10 @@ int rdma_alloc_commit_uobject(struct ib_uobject *uobj) return ret; } + /* matches atomic_set(-1) in alloc_uobj */ + lockdep_check(uobj, true); + atomic_set(&uobj->usecnt, 0); + uobj->type->type_class->alloc_commit(uobj); up_read(&uobj->context->cleanup_rwsem);