Re: [bug report] io_uring: add support for sqe links

[Jens Axboe <axboe@kernel.dk>]

On 5/27/19 4:08 AM, Dan Carpenter wrote:
> Hello Jens Axboe,
> 
> The patch f3fafe4103bd: "io_uring: add support for sqe links" from
> May 10, 2019, leads to the following static checker warning:
> 
> 	fs/io_uring.c:623 io_req_link_next()
> 	error: potential NULL dereference 'nxt'.
> 
> fs/io_uring.c
>     614  static void io_req_link_next(struct io_kiocb *req)
>     615  {
>     616          struct io_kiocb *nxt;
>     617
>     618          nxt = list_first_entry_or_null(&req->link_list, struct io_kiocb, list);
>     619          list_del(&nxt->list);
>                            ^^^^^^^^^
> The warning is a false positive but this is a NULL dereference.
> 
>     620          if (!list_empty(&req->link_list)) {
>     621                  INIT_LIST_HEAD(&nxt->link_list);
>                                          ^^^^^
> False positive.

Both of them are false positives. I can work around them though, as it
probably makes it a bit cleaner, too.

> 
>     622                  list_splice(&req->link_list, &nxt->link_list);
>     623                  nxt->flags |= REQ_F_LINK;
>     624          }
>     625
>     626          INIT_WORK(&nxt->work, io_sq_wq_submit_work);
>                            ^^^^^^^^^^
>     627          queue_work(req->ctx->sqo_wq, &nxt->work);
>                                               ^^^^^^^^^^
> Other bugs.

Not sure what that means?


-- 
Jens Axboe