io_uring: fix deferred req iovec leak

After defer, a request will be prepared, that includes allocating iovec
if needed, and then submitted through io_wq_submit_work() but not custom
handler (e.g. io_rw_async()/io_sendrecv_async()). However, it'll leak
iovec, as it's in io-wq and the code goes as follows:

io_read() {
	if (!io_wq_current_is_worker())
		kfree(iovec);
}

Put all deallocation logic in io_{read,write,send,recv}(), which will
leave the memory, if going async with -EAGAIN.

It also fixes a leak after failed io_alloc_async_ctx() in
io_{recv,send}_msg().

Cc: stable@vger.kernel.org # 5.5
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -2144,17 +2144,6 @@ static int io_alloc_async_ctx(struct io_kiocb *req)
 	return req->io == NULL;
 }
 
-static void io_rw_async(struct io_wq_work **workptr)
-{
-	struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
-	struct iovec *iov = NULL;
-
-	if (req->io->rw.iov != req->io->rw.fast_iov)
-		iov = req->io->rw.iov;
-	io_wq_submit_work(workptr);
-	kfree(iov);
-}
-
 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)
@@ -2167,7 +2156,6 @@ static int io_setup_async_rw(struct io_kiocb *req, ssize_t io_size,
 
 		io_req_map_rw(req, io_size, iovec, fast_iov, iter);
 	}
-	req->work.func = io_rw_async;
 	return 0;
 }
 
@@ -2254,8 +2242,7 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
 		}
 	}
 out_free:
-	if (!io_wq_current_is_worker())
-		kfree(iovec);
+	kfree(iovec);
 	return ret;
 }
 
@@ -2360,8 +2347,7 @@ static int io_write(struct io_kiocb *req, struct io_kiocb **nxt,
 		}
 	}
 out_free:
-	if (!io_wq_current_is_worker())
-		kfree(iovec);
+	kfree(iovec);
 	return ret;
 }
 
@@ -2956,19 +2942,6 @@ static int io_sync_file_range(struct io_kiocb *req, struct io_kiocb **nxt,
 	return 0;
 }
 
-#if defined(CONFIG_NET)
-static void io_sendrecv_async(struct io_wq_work **workptr)
-{
-	struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
-	struct iovec *iov = NULL;
-
-	if (req->io->rw.iov != req->io->rw.fast_iov)
-		iov = req->io->msg.iov;
-	io_wq_submit_work(workptr);
-	kfree(iov);
-}
-#endif
-
 static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 #if defined(CONFIG_NET)
@@ -3037,17 +3010,19 @@ static int io_sendmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 		if (force_nonblock && ret == -EAGAIN) {
 			if (req->io)
 				return -EAGAIN;
-			if (io_alloc_async_ctx(req))
+			if (io_alloc_async_ctx(req)) {
+				if (kmsg && kmsg->iov != kmsg->fast_iov)
+					kfree(kmsg->iov);
 				return -ENOMEM;
+			}
 			memcpy(&req->io->msg, &io.msg, sizeof(io.msg));
-			req->work.func = io_sendrecv_async;
 			return -EAGAIN;
 		}
 		if (ret == -ERESTARTSYS)
 			ret = -EINTR;
 	}
 
-	if (!io_wq_current_is_worker() && kmsg && kmsg->iov != kmsg->fast_iov)
+	if (kmsg && kmsg->iov != kmsg->fast_iov)
 		kfree(kmsg->iov);
 	io_cqring_add_event(req, ret);
 	if (ret < 0)
@@ -3181,17 +3156,19 @@ static int io_recvmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 		if (force_nonblock && ret == -EAGAIN) {
 			if (req->io)
 				return -EAGAIN;
-			if (io_alloc_async_ctx(req))
+			if (io_alloc_async_ctx(req)) {
+				if (kmsg && kmsg->iov != kmsg->fast_iov)
+					kfree(kmsg->iov);
 				return -ENOMEM;
+			}
 			memcpy(&req->io->msg, &io.msg, sizeof(io.msg));
-			req->work.func = io_sendrecv_async;
 			return -EAGAIN;
 		}
 		if (ret == -ERESTARTSYS)
 			ret = -EINTR;
 	}
 
-	if (!io_wq_current_is_worker() && kmsg && kmsg->iov != kmsg->fast_iov)
+	if (kmsg && kmsg->iov != kmsg->fast_iov)
 		kfree(kmsg->iov);
 	io_cqring_add_event(req, ret);
 	if (ret < 0)