linux-kernel - [PATCH 4.9 29/35] usb: gadget: serial: fix oops when data rxd after close

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Date:   Thu, 18 Oct 2018 19:54:58 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stephen Warren <swarren@...dia.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Krzysztof Kozlowski <krzk@...nel.org>
Subject: [PATCH 4.9 29/35] usb: gadget: serial: fix oops when data rxd after close

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stephen Warren <swarren@...dia.com>

commit daa35bd95634a2a2d72d1049c93576a02711cb1a upstream.

When the gadget serial device has no associated TTY, do not pass any
received data into the TTY layer for processing; simply drop it instead.
This prevents the TTY layer from calling back into the gadget serial
driver, which will then crash in e.g. gs_write_room() due to lack of
gadget serial device to TTY association (i.e. a NULL pointer dereference).

Signed-off-by: Stephen Warren <swarren@...dia.com>
Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -537,7 +537,7 @@ static void gs_rx_push(unsigned long _po
 		}
 
 		/* push data to (open) tty */
-		if (req->actual) {
+		if (req->actual && tty) {
 			char		*packet = req->buf;
 			unsigned	size = req->actual;
 			unsigned	n;