linux-kernel - [PATCH 4.9 002/199] usb: gadget: u_serial: add missing port entry locking

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Date:   Thu, 19 Dec 2019 19:31:24 +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,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Ladislav Michl <ladis@...ux-mips.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>
Subject: [PATCH 4.9 002/199] usb: gadget: u_serial: add missing port entry locking

From: Michał Mirosław <mirq-linux@...e.qmqm.pl>

commit daf82bd24e308c5a83758047aff1bd81edda4f11 upstream.

gserial_alloc_line() misses locking (for a release barrier) while
resetting port entry on TTY allocation failure. Fix this.

Cc: stable@...r.kernel.org
Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Tested-by: Ladislav Michl <ladis@...ux-mips.org>
Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/gadget/function/u_serial.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1391,8 +1391,10 @@ int gserial_alloc_line(unsigned char *li
 				__func__, port_num, PTR_ERR(tty_dev));
 
 		ret = PTR_ERR(tty_dev);
+		mutex_lock(&ports[port_num].lock);
 		port = ports[port_num].port;
 		ports[port_num].port = NULL;
+		mutex_unlock(&ports[port_num].lock);
 		gserial_free_port(port);
 		goto err;
 	}