Merge tag 'io_uring-5.14-2021-07-30' of git://git.kernel.dk/linux-block

Pull io_uring fixes from Jens Axboe:

 - A fix for block backed reissue (me)

 - Reissue context hardening (me)

 - Async link locking fix (Pavel)

* tag 'io_uring-5.14-2021-07-30' of git://git.kernel.dk/linux-block:
  io_uring: fix poll requests leaking second poll entries
  io_uring: don't block level reissue off completion path
  io_uring: always reissue from task_work context
  io_uring: fix race in unified task_work running
  io_uring: fix io_prep_async_link locking

Author: torvalds

fs/io_uring.c

@@ -1279,8 +1279,17 @@ static void io_prep_async_link(struct io_kiocb *req)
 {
 	struct io_kiocb *cur;
 
-	io_for_each_link(cur, req)
-		io_prep_async_work(cur);
+	if (req->flags & REQ_F_LINK_TIMEOUT) {
+		struct io_ring_ctx *ctx = req->ctx;
+
+		spin_lock_irq(&ctx->completion_lock);
+		io_for_each_link(cur, req)
+			io_prep_async_work(cur);
+		spin_unlock_irq(&ctx->completion_lock);
+	} else {
+		io_for_each_link(cur, req)
+			io_prep_async_work(cur);
+	}
 }
 
 static void io_queue_async_work(struct io_kiocb *req)
@@ -1950,9 +1959,13 @@ static void tctx_task_work(struct callback_head *cb)
 			node = next;
 		}
 		if (wq_list_empty(&tctx->task_list)) {
+			spin_lock_irq(&tctx->task_lock);
 			clear_bit(0, &tctx->task_state);
-			if (wq_list_empty(&tctx->task_list))
+			if (wq_list_empty(&tctx->task_list)) {
+				spin_unlock_irq(&tctx->task_lock);
 				break;
+			}
+			spin_unlock_irq(&tctx->task_lock);
 			/* another tctx_task_work() is enqueued, yield */
 			if (test_and_set_bit(0, &tctx->task_state))
 				break;
@@ -2047,6 +2060,12 @@ static void io_req_task_queue(struct io_kiocb *req)
 	io_req_task_work_add(req);
 }
 
+static void io_req_task_queue_reissue(struct io_kiocb *req)
+{
+	req->io_task_work.func = io_queue_async_work;
+	io_req_task_work_add(req);
+}
+
 static inline void io_queue_next(struct io_kiocb *req)
 {
 	struct io_kiocb *nxt = io_req_find_next(req);
@@ -2235,7 +2254,7 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
 		    !(req->flags & REQ_F_DONT_REISSUE)) {
 			req->iopoll_completed = 0;
 			req_ref_get(req);
-			io_queue_async_work(req);
+			io_req_task_queue_reissue(req);
 			continue;
 		}
 
@@ -2428,6 +2447,12 @@ static bool io_rw_should_reissue(struct io_kiocb *req)
 	 */
 	if (percpu_ref_is_dying(&ctx->refs))
 		return false;
+	/*
+	 * Play it safe and assume not safe to re-import and reissue if we're
+	 * not in the original thread group (or in task context).
+	 */
+	if (!same_thread_group(req->task, current) || !in_task())
+		return false;
 	return true;
 }
 #else
@@ -2758,7 +2783,7 @@ static void kiocb_done(struct kiocb *kiocb, ssize_t ret,
 		req->flags &= ~REQ_F_REISSUE;
 		if (io_resubmit_prep(req)) {
 			req_ref_get(req);
-			io_queue_async_work(req);
+			io_req_task_queue_reissue(req);
 		} else {
 			int cflags = 0;
 
@@ -4914,7 +4939,6 @@ static bool io_poll_complete(struct io_kiocb *req, __poll_t mask)
 	if (req->poll.events & EPOLLONESHOT)
 		flags = 0;
 	if (!io_cqring_fill_event(ctx, req->user_data, error, flags)) {
-		io_poll_remove_waitqs(req);
 		req->poll.done = true;
 		flags = 0;
 	}
@@ -4937,6 +4961,7 @@ static void io_poll_task_func(struct io_kiocb *req)
 
 		done = io_poll_complete(req, req->result);
 		if (done) {
+			io_poll_remove_double(req);
 			hash_del(&req->hash_node);
 		} else {
 			req->result = 0;
@@ -5124,7 +5149,7 @@ static __poll_t __io_arm_poll_handler(struct io_kiocb *req,
 		ipt->error = -EINVAL;
 
 	spin_lock_irq(&ctx->completion_lock);
-	if (ipt->error)
+	if (ipt->error || (mask && (poll->events & EPOLLONESHOT)))
 		io_poll_remove_double(req);
 	if (likely(poll->head)) {
 		spin_lock(&poll->head->lock);
@@ -5196,7 +5221,6 @@ static int io_arm_poll_handler(struct io_kiocb *req)
 	ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask,
 					io_async_wake);
 	if (ret || ipt.error) {
-		io_poll_remove_double(req);
 		spin_unlock_irq(&ctx->completion_lock);
 		if (ret)
 			return IO_APOLL_READY;