io_uring: don't set COMP_LOCKED if won't put

__io_kill_linked_timeout() sets REQ_F_COMP_LOCKED for a linked timeout
even if it can't cancel it, e.g. it's already running. It not only races
with io_link_timeout_fn() for ->flags field, but also leaves the flag
set and so io_link_timeout_fn() may find it and decide that it holds the
lock. Hopefully, the second problem is potential.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 717dd5d..f0f4b5b 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1769,6 +1769,7 @@ static bool io_link_cancel_timeout(struct io_kiocb *req)
 
        ret = hrtimer_try_to_cancel(&io->timer);
        if (ret != -1) {
 
        ret = hrtimer_try_to_cancel(&io->timer);
        if (ret != -1) {

+               req->flags |= REQ_F_COMP_LOCKED;

                io_cqring_fill_event(req, -ECANCELED);
                io_commit_cqring(ctx);
                req->flags &= ~REQ_F_LINK_HEAD;
                io_cqring_fill_event(req, -ECANCELED);
                io_commit_cqring(ctx);
                req->flags &= ~REQ_F_LINK_HEAD;


@@ -1791,7 +1792,6 @@ static bool __io_kill_linked_timeout(struct io_kiocb *req)
                return false;
 
        list_del_init(&link->link_list);
                return false;
 
        list_del_init(&link->link_list);

-       link->flags |= REQ_F_COMP_LOCKED;

        wake_ev = io_link_cancel_timeout(link);
        req->flags &= ~REQ_F_LINK_TIMEOUT;
        return wake_ev;
        wake_ev = io_link_cancel_timeout(link);
        req->flags &= ~REQ_F_LINK_TIMEOUT;
        return wake_ev;