User space can hold a tty open indefinitely and tty drivers must not release the underlying structures until the last user is gone.

Switch to using the tty-port reference counter to manage the life time of the greybus tty state to avoid use after free after a disconnect.

Fixes: a18e15175708 ("greybus: more uart work") Cc: stable@vger.kernel.org # 4.9 Signed-off-by: Johan Hovold johan@kernel.org --- drivers/staging/greybus/uart.c | 62 ++++++++++++++++++---------------- 1 file changed, 32 insertions(+), 30 deletions(-)

diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c index 73f01ed1e5b7..a943fce322be 100644 --- a/drivers/staging/greybus/uart.c +++ b/drivers/staging/greybus/uart.c @@ -761,6 +761,17 @@ static void gb_tty_port_shutdown(struct tty_port *port) gbphy_runtime_put_autosuspend(gb_tty->gbphy_dev); }

+static void gb_tty_port_destruct(struct tty_port *port) +{ + struct gb_tty *gb_tty = container_of(port, struct gb_tty, port); + + if (gb_tty->minor != GB_NUM_MINORS) + release_minor(gb_tty); + kfifo_free(&gb_tty->write_fifo); + kfree(gb_tty->buffer); + kfree(gb_tty); +} + static const struct tty_operations gb_ops = { .install = gb_tty_install, .open = gb_tty_open, @@ -786,6 +797,7 @@ static const struct tty_port_operations gb_port_ops = { .dtr_rts = gb_tty_dtr_rts, .activate = gb_tty_port_activate, .shutdown = gb_tty_port_shutdown, + .destruct = gb_tty_port_destruct, };

static int gb_uart_probe(struct gbphy_device *gbphy_dev, @@ -798,17 +810,11 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev, int retval; int minor;

- gb_tty = kzalloc(sizeof(*gb_tty), GFP_KERNEL); - if (!gb_tty) - return -ENOMEM; - connection = gb_connection_create(gbphy_dev->bundle, le16_to_cpu(gbphy_dev->cport_desc->id), gb_uart_request_handler); - if (IS_ERR(connection)) { - retval = PTR_ERR(connection); - goto exit_tty_free; - } + if (IS_ERR(connection)) + return PTR_ERR(connection);

max_payload = gb_operation_get_payload_size_max(connection); if (max_payload < sizeof(struct gb_uart_send_data_request)) { @@ -816,13 +822,23 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev, goto exit_connection_destroy; }

+ gb_tty = kzalloc(sizeof(*gb_tty), GFP_KERNEL); + if (!gb_tty) { + retval = -ENOMEM; + goto exit_connection_destroy; + } + + tty_port_init(&gb_tty->port); + gb_tty->port.ops = &gb_port_ops; + gb_tty->minor = GB_NUM_MINORS; + gb_tty->buffer_payload_max = max_payload - sizeof(struct gb_uart_send_data_request);

gb_tty->buffer = kzalloc(gb_tty->buffer_payload_max, GFP_KERNEL); if (!gb_tty->buffer) { retval = -ENOMEM; - goto exit_connection_destroy; + goto exit_put_port; }

INIT_WORK(&gb_tty->tx_work, gb_uart_tx_write_work); @@ -830,7 +846,7 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev, retval = kfifo_alloc(&gb_tty->write_fifo, GB_UART_WRITE_FIFO_SIZE, GFP_KERNEL); if (retval) - goto exit_buf_free; + goto exit_put_port;

gb_tty->credits = GB_UART_FIRMWARE_CREDITS; init_completion(&gb_tty->credits_complete); @@ -844,7 +860,7 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev, } else { retval = minor; } - goto exit_kfifo_free; + goto exit_put_port; }

gb_tty->minor = minor; @@ -853,9 +869,6 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev, init_waitqueue_head(&gb_tty->wioctl); mutex_init(&gb_tty->mutex);

- tty_port_init(&gb_tty->port); - gb_tty->port.ops = &gb_port_ops; - gb_tty->connection = connection; gb_tty->gbphy_dev = gbphy_dev; gb_connection_set_data(connection, gb_tty); @@ -863,7 +876,7 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev,

retval = gb_connection_enable_tx(connection); if (retval) - goto exit_release_minor; + goto exit_put_port;

send_control(gb_tty, gb_tty->ctrlout);

@@ -890,16 +903,10 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev,

exit_connection_disable: gb_connection_disable(connection); -exit_release_minor: - release_minor(gb_tty); -exit_kfifo_free: - kfifo_free(&gb_tty->write_fifo); -exit_buf_free: - kfree(gb_tty->buffer); +exit_put_port: + tty_port_put(&gb_tty->port); exit_connection_destroy: gb_connection_destroy(connection); -exit_tty_free: - kfree(gb_tty);

return retval; } @@ -930,15 +937,10 @@ static void gb_uart_remove(struct gbphy_device *gbphy_dev) gb_connection_disable_rx(connection); tty_unregister_device(gb_tty_driver, gb_tty->minor);

- /* FIXME - free transmit / receive buffers */ - gb_connection_disable(connection); - tty_port_destroy(&gb_tty->port); gb_connection_destroy(connection); - release_minor(gb_tty); - kfifo_free(&gb_tty->write_fifo); - kfree(gb_tty->buffer); - kfree(gb_tty); + + tty_port_put(&gb_tty->port); }

static int gb_tty_init(void)