On 11/20/19 1:44 AM, Pavel Begunkov wrote: > On 11/20/2019 1:33 AM, Jens Axboe wrote: >> We currently clear the linked timeout field if we cancel such a timeout, >> but we should only attempt to cancel if it's the first one we see. >> Others should simply be freed like other requests, as they haven't >> been started yet. >> >> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> >> >> --- >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index a79ef43367b1..d1085e4e8ae9 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -937,12 +937,12 @@ static void io_fail_links(struct io_kiocb *req) >> if ((req->flags & REQ_F_LINK_TIMEOUT) && >> link->submit.sqe->opcode == IORING_OP_LINK_TIMEOUT) { >> io_link_cancel_timeout(link); >> - req->flags &= ~REQ_F_LINK_TIMEOUT; >> } else { >> io_cqring_fill_event(link, -ECANCELED); >> __io_double_put_req(link); >> } >> kfree(sqe_to_free); >> + req->flags &= ~REQ_F_LINK_TIMEOUT; > > That's not necessary, but maybe would safer to keep. If > REQ_F_LINK_TIMEOUT is set, than there was a link timeout request, > and for it and only for it io_link_cancel_timeout() will be called. > > However, this is only true if linked timeout isn't fired. Otherwise, > there is another bug, which isn't fixed by either of the patches. We > need to clear REQ_F_LINK_TIMEOUT in io_link_timeout_fn() as well. > > Let: REQ -> L_TIMEOUT1 -> L_TIMEOUT2 > 1. L_TIMEOUT1 fired before REQ is completed > > 2. io_link_timeout_fn() removes L_TIMEOUT1 from the list: > REQ|REQ_F_LINK_TIMEOUT -> L_TIMEOUT2 > > 3. free_req(REQ) then call io_link_cancel_timeout(L_TIMEOUT2) > leaking it (as described in my patch). > > P.S. haven't tried to test nor reproduce it yet. That's exactly the case I was worried about. In any case, it seems prudent to handle it defensively. -- Jens Axboe