Merge tag 'io_uring-5.5-2020-01-16' of git://git.kernel.dk/linux-block

Pull io_uring fixes form Jens Axboe:

 - Ensure ->result is always set when IO is retried (Bijan)

 - In conjunction with the above, fix a regression in polled IO issue
   when retried (me/Bijan)

 - Don't setup async context for read/write fixed, otherwise we may
   wrongly map the iovec on retry (me)

 - Cancel io-wq work if we fail getting mm reference (me)

 - Ensure dependent work is always initialized correctly (me)

 - Only allow original task to submit IO, don't allow it from a passed
   ring fd (me)

* tag 'io_uring-5.5-2020-01-16' of git://git.kernel.dk/linux-block:
  io_uring: only allow submit from owning task
  io_uring: ensure workqueue offload grabs ring mutex for poll list
  io_uring: clear req->result always before issuing a read/write request
  io_uring: be consistent in assigning next work from handler
  io-wq: cancel work if we fail getting a mm reference
  io_uring: don't setup async context for read/write fixed

fs/io-wq.c

@@ -445,10 +445,14 @@ static void io_worker_handle_work(struct io_worker *worker)
 			task_unlock(current);
 		}
 		if ((work->flags & IO_WQ_WORK_NEEDS_USER) && !worker->mm &&
-		    wq->mm && mmget_not_zero(wq->mm)) {
-			use_mm(wq->mm);
-			set_fs(USER_DS);
-			worker->mm = wq->mm;
+		    wq->mm) {
+			if (mmget_not_zero(wq->mm)) {
+				use_mm(wq->mm);
+				set_fs(USER_DS);
+				worker->mm = wq->mm;
+			} else {
+				work->flags |= IO_WQ_WORK_CANCEL;
+			}
 		}
 		if (!worker->creds)
 			worker->creds = override_creds(wq->creds);

fs/io_uring.c

@@ -1786,6 +1786,9 @@ static int io_setup_async_rw(struct io_kiocb *req, ssize_t io_size,
 			     struct iovec *iovec, struct iovec *fast_iov,
 			     struct iov_iter *iter)
 {
+	if (req->opcode == IORING_OP_READ_FIXED ||
+	    req->opcode == IORING_OP_WRITE_FIXED)
+		return 0;
 	if (!req->io && io_alloc_async_ctx(req))
 		return -ENOMEM;
 
@@ -1840,6 +1843,7 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
 	if (!force_nonblock)
 		req->rw.kiocb.ki_flags &= ~IOCB_NOWAIT;
 
+	req->result = 0;
 	io_size = ret;
 	if (req->flags & REQ_F_LINK)
 		req->result = io_size;
@@ -1927,6 +1931,7 @@ static int io_write(struct io_kiocb *req, struct io_kiocb **nxt,
 	if (!force_nonblock)
 		req->rw.kiocb.ki_flags &= ~IOCB_NOWAIT;
 
+	req->result = 0;
 	io_size = ret;
 	if (req->flags & REQ_F_LINK)
 		req->result = io_size;
@@ -2034,6 +2039,28 @@ static bool io_req_cancelled(struct io_kiocb *req)
 	return false;
 }
 
+static void io_link_work_cb(struct io_wq_work **workptr)
+{
+	struct io_wq_work *work = *workptr;
+	struct io_kiocb *link = work->data;
+
+	io_queue_linked_timeout(link);
+	work->func = io_wq_submit_work;
+}
+
+static void io_wq_assign_next(struct io_wq_work **workptr, struct io_kiocb *nxt)
+{
+	struct io_kiocb *link;
+
+	io_prep_async_work(nxt, &link);
+	*workptr = &nxt->work;
+	if (link) {
+		nxt->work.flags |= IO_WQ_WORK_CB;
+		nxt->work.func = io_link_work_cb;
+		nxt->work.data = link;
+	}
+}
+
 static void io_fsync_finish(struct io_wq_work **workptr)
 {
 	struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
@@ -2052,7 +2079,7 @@ static void io_fsync_finish(struct io_wq_work **workptr)
 	io_cqring_add_event(req, ret);
 	io_put_req_find_next(req, &nxt);
 	if (nxt)
-		*workptr = &nxt->work;
+		io_wq_assign_next(workptr, nxt);
 }
 
 static int io_fsync(struct io_kiocb *req, struct io_kiocb **nxt,
@@ -2108,7 +2135,7 @@ static void io_sync_file_range_finish(struct io_wq_work **workptr)
 	io_cqring_add_event(req, ret);
 	io_put_req_find_next(req, &nxt);
 	if (nxt)
-		*workptr = &nxt->work;
+		io_wq_assign_next(workptr, nxt);
 }
 
 static int io_sync_file_range(struct io_kiocb *req, struct io_kiocb **nxt,
@@ -2374,7 +2401,7 @@ static void io_accept_finish(struct io_wq_work **workptr)
 		return;
 	__io_accept(req, &nxt, false);
 	if (nxt)
-		*workptr = &nxt->work;
+		io_wq_assign_next(workptr, nxt);
 }
 #endif
 
@@ -2605,7 +2632,7 @@ static void io_poll_complete_work(struct io_wq_work **workptr)
 		req_set_fail_links(req);
 	io_put_req_find_next(req, &nxt);
 	if (nxt)
-		*workptr = &nxt->work;
+		io_wq_assign_next(workptr, nxt);
 }
 
 static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
@@ -3259,24 +3286,24 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 		return ret;
 
 	if (ctx->flags & IORING_SETUP_IOPOLL) {
+		const bool in_async = io_wq_current_is_worker();
+
 		if (req->result == -EAGAIN)
 			return -EAGAIN;
 
+		/* workqueue context doesn't hold uring_lock, grab it now */
+		if (in_async)
+			mutex_lock(&ctx->uring_lock);
+
 		io_iopoll_req_issued(req);
+
+		if (in_async)
+			mutex_unlock(&ctx->uring_lock);
 	}
 
 	return 0;
 }
 
-static void io_link_work_cb(struct io_wq_work **workptr)
-{
-	struct io_wq_work *work = *workptr;
-	struct io_kiocb *link = work->data;
-
-	io_queue_linked_timeout(link);
-	work->func = io_wq_submit_work;
-}
-
 static void io_wq_submit_work(struct io_wq_work **workptr)
 {
 	struct io_wq_work *work = *workptr;
@@ -3313,17 +3340,8 @@ static void io_wq_submit_work(struct io_wq_work **workptr)
 	}
 
 	/* if a dependent link is ready, pass it back */
-	if (!ret && nxt) {
-		struct io_kiocb *link;
-
-		io_prep_async_work(nxt, &link);
-		*workptr = &nxt->work;
-		if (link) {
-			nxt->work.flags |= IO_WQ_WORK_CB;
-			nxt->work.func = io_link_work_cb;
-			nxt->work.data = link;
-		}
-	}
+	if (!ret && nxt)
+		io_wq_assign_next(workptr, nxt);
 }
 
 static bool io_req_op_valid(int op)
@@ -5141,6 +5159,12 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 	} else if (to_submit) {
 		struct mm_struct *cur_mm;
 
+		if (current->mm != ctx->sqo_mm ||
+		    current_cred() != ctx->creds) {
+			ret = -EPERM;
+			goto out;
+		}
+
 		to_submit = min(to_submit, ctx->sq_entries);
 		mutex_lock(&ctx->uring_lock);
 		/* already have mm, so io_submit_sqes() won't try to grab it */