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Message-Id: <20171212123443.987739974@linuxfoundation.org> Date: Tue, 12 Dec 2017 13:43:03 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Johan Hovold <johan@...nel.org> Subject: [PATCH 4.14 003/164] serdev: ttyport: add missing receive_buf sanity checks 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johan Hovold <johan@...nel.org> commit eb281683621b71ab9710d9dccbbef0c2e1769c97 upstream. The receive_buf tty-port callback should return the number of bytes accepted and must specifically never return a negative errno (or a value larger than the buffer size) to the tty layer. A serdev driver not providing a receive_buf callback would currently cause the flush_to_ldisc() worker to spin in a tight loop when the tty buffer pointers are incremented with -EINVAL (-22) after data has been received. A serdev driver occasionally returning a negative errno (or a too large byte count) could cause information leaks or crashes when accessing memory outside the tty buffers in consecutive callbacks. Fixes: cd6484e1830b ("serdev: Introduce new bus for serial attached devices") Signed-off-by: Johan Hovold <johan@...nel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/tty/serdev/serdev-ttyport.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) --- a/drivers/tty/serdev/serdev-ttyport.c +++ b/drivers/tty/serdev/serdev-ttyport.c @@ -35,11 +35,22 @@ static int ttyport_receive_buf(struct tt { struct serdev_controller *ctrl = port->client_data; struct serport *serport = serdev_controller_get_drvdata(ctrl); + int ret; if (!test_bit(SERPORT_ACTIVE, &serport->flags)) return 0; - return serdev_controller_receive_buf(ctrl, cp, count); + ret = serdev_controller_receive_buf(ctrl, cp, count); + + dev_WARN_ONCE(&ctrl->dev, ret < 0 || ret > count, + "receive_buf returns %d (count = %zu)\n", + ret, count); + if (ret < 0) + return 0; + else if (ret > count) + return count; + + return ret; } static void ttyport_write_wakeup(struct tty_port *port)
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