2021-09-28 12:06:41

by Johan Hovold

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: [email protected] # 4.16
Cc: Lu Baolu <[email protected]>
Signed-off-by: Johan Hovold <[email protected]>
---
drivers/usb/host/xhci-dbgtty.c | 28 +++++++++++++---------------
1 file changed, 13 insertions(+), 15 deletions(-)

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);
--
2.32.0

2021-09-30 13:00:08

by Mathias Nyman

Subject: Re: [PATCH] USB: xhci: dbc: fix tty registration race

On 28.9.2021 15.04, Johan Hovold wrote:
> 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: [email protected] # 4.16
> Cc: Lu Baolu <[email protected]>
> Signed-off-by: Johan Hovold <[email protected]>

Thanks, adding to queue

-Mathias