From: Xiaoguang Wang xiaoguang.wang@linux.alibaba.com
commit c07e6719511e77c4b289f62bfe96423eb6ea061d upstream.
io_iopoll_complete() does not hold completion_lock to complete polled io, so in io_wq_submit_work(), we can not call io_req_complete() directly, to complete polled io, otherwise there maybe concurrent access to cqring, defer_list, etc, which is not safe. Commit dad1b1242fd5 ("io_uring: always let io_iopoll_complete() complete polled io") has fixed this issue, but Pavel reported that IOPOLL apart from rw can do buf reg/unreg requests( IORING_OP_PROVIDE_BUFFERS or IORING_OP_REMOVE_BUFFERS), so the fix is not good.
Given that io_iopoll_complete() is always called under uring_lock, so here for polled io, we can also get uring_lock to fix this issue.
Fixes: dad1b1242fd5 ("io_uring: always let io_iopoll_complete() complete polled io") Cc: stable@vger.kernel.org # 5.5+ Signed-off-by: Xiaoguang Wang xiaoguang.wang@linux.alibaba.com Reviewed-by: Pavel Begunkov asml.silence@gmail.com [axboe: don't deref 'req' after completing it'] Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/io_uring.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -6081,19 +6081,28 @@ static struct io_wq_work *io_wq_submit_w }
if (ret) { + struct io_ring_ctx *lock_ctx = NULL; + + if (req->ctx->flags & IORING_SETUP_IOPOLL) + lock_ctx = req->ctx; + /* - * io_iopoll_complete() does not hold completion_lock to complete - * polled io, so here for polled io, just mark it done and still let - * io_iopoll_complete() complete it. + * io_iopoll_complete() does not hold completion_lock to + * complete polled io, so here for polled io, we can not call + * io_req_complete() directly, otherwise there maybe concurrent + * access to cqring, defer_list, etc, which is not safe. Given + * that io_iopoll_complete() is always called under uring_lock, + * so here for polled io, we also get uring_lock to complete + * it. */ - if (req->ctx->flags & IORING_SETUP_IOPOLL) { - struct kiocb *kiocb = &req->rw.kiocb; + if (lock_ctx) + mutex_lock(&lock_ctx->uring_lock); + + req_set_fail_links(req); + io_req_complete(req, ret);
- kiocb_done(kiocb, ret, NULL); - } else { - req_set_fail_links(req); - io_req_complete(req, ret); - } + if (lock_ctx) + mutex_unlock(&lock_ctx->uring_lock); }
return io_steal_work(req);