The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 880de403777376e50bdf60def359fa50a722006f Mon Sep 17 00:00:00 2001
From: Johan Hovold johan@kernel.org Date: Fri, 8 Oct 2021 12:25:45 +0300 Subject: [PATCH] USB: xhci: dbc: fix tty registration race
Make sure to allocate resources before registering the tty device to avoid having a racing open() and write() fail to enable rx or dereference a NULL pointer when accessing the uninitialised fifo.
Fixes: dfba2174dc42 ("usb: xhci: Add DbC support in xHCI driver") Cc: stable@vger.kernel.org # 4.16 Cc: Lu Baolu baolu.lu@linux.intel.com Signed-off-by: Johan Hovold johan@kernel.org Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com Link: https://lore.kernel.org/r/20211008092547.3996295-4-mathias.nyman@linux.intel... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c index 6e784f2fc26d..eb46e642e87a 100644 --- a/drivers/usb/host/xhci-dbgtty.c +++ b/drivers/usb/host/xhci-dbgtty.c @@ -408,40 +408,38 @@ static int xhci_dbc_tty_register_device(struct xhci_dbc *dbc) return -EBUSY;
xhci_dbc_tty_init_port(dbc, port); - tty_dev = tty_port_register_device(&port->port, - dbc_tty_driver, 0, NULL); - if (IS_ERR(tty_dev)) { - ret = PTR_ERR(tty_dev); - goto register_fail; - }
ret = kfifo_alloc(&port->write_fifo, DBC_WRITE_BUF_SIZE, GFP_KERNEL); if (ret) - goto buf_alloc_fail; + goto err_exit_port;
ret = xhci_dbc_alloc_requests(dbc, BULK_IN, &port->read_pool, dbc_read_complete); if (ret) - goto request_fail; + goto err_free_fifo;
ret = xhci_dbc_alloc_requests(dbc, BULK_OUT, &port->write_pool, dbc_write_complete); if (ret) - goto request_fail; + goto err_free_requests; + + tty_dev = tty_port_register_device(&port->port, + dbc_tty_driver, 0, NULL); + if (IS_ERR(tty_dev)) { + ret = PTR_ERR(tty_dev); + goto err_free_requests; + }
port->registered = true;
return 0;
-request_fail: +err_free_requests: xhci_dbc_free_requests(&port->read_pool); xhci_dbc_free_requests(&port->write_pool); +err_free_fifo: kfifo_free(&port->write_fifo); - -buf_alloc_fail: - tty_unregister_device(dbc_tty_driver, 0); - -register_fail: +err_exit_port: xhci_dbc_tty_exit_port(port);
dev_err(dbc->dev, "can't register tty port, err %d\n", ret);