usb: gadget: u_serial: check Null pointer in EP callback

[Daehwan Jung <dh10.jung@samsung.com>]

From: taehyun cho <taehyun.cho@samsung.com>

Endpoint complete function in u_serial can be executed
when 'gs_port' is Null. This situation happens when
'dwc3_gadget_pullup' returns ETIMEDOUT. The reason why
ETIMEDOUT is returned is that whole system is out of order
including interrupt regardless of USB.

pc : __lock_acquire+0x54/0x5ec
lr : lock_acquire+0xe8/0x198
sp : ffffffc03914b9d0
x29: ffffffc03914b9d0 x28: ffffff895f13b680
x27: 0000000000000000 x26: 0000000000000000
x25: 00000000000003c8 x24: 0000000000000080
x23: ffffffc010a8f650 x22: 0000000000000000
x21: 0000000000000000 x20: 0000000000000000
x19: ffffffc010a8f650 x18: ffffffc02d70a0b0
x17: 0000000000000000 x16: 00000000000229e0
x15: 0000000000000004 x14: 00000000000004f2
x13: ffffffc0120fe178 x12: 0000000000000003
x11: 00000000ffffffff x10: 0000000100000001
x9 : 0000000000000001 x8 : 00000000000003c8
x7 : 0000000000000000 x6 : ffffffc010a8f650
x5 : 0000000000000000 x4 : 0000000000000080
x3 : 0000000000000000 x2 : 0000000000000000
x1 : 0000000000000000 x0 : 00000000000003c8
Call trace:
 __lock_acquire+0x54/0x5ec
 lock_acquire+0xe8/0x198
 _raw_spin_lock+0x70/0x88
 gs_read_complete+0x48/0xac
 usb_gadget_giveback_request+0x48/0x80
 dwc3_gadget_giveback+0xcc/0xe8
 dwc3_remove_requests+0xa8/0x188
 __dwc3_gadget_ep_disable+0x98/0x110
 dwc3_gadget_ep_disable+0x50/0xbc
 usb_ep_disable+0x44/0x94
 gserial_disconnect+0xc0/0x250
 acm_free_func+0x30/0x48
 usb_put_function+0x34/0x68
 config_usb_cfg_unlink+0xdc/0xf8
 configfs_unlink+0x144/0x264
 vfs_unlink+0x134/0x218
 do_unlinkat+0x13c/0x2a0
 __arm64_sys_unlinkat+0x48/0x60
 el0_svc_common.llvm.10277270529376503802+0xb8/0x1b4
 do_el0_svc+0x24/0x8c
 el0_svc+0x10/0x1c
 el0_sync_handler+0x68/0xac
 el0_sync+0x18c/0x1c0

Signed-off-by: taehyun cho <taehyun.cho@samsung.com>
---
 drivers/usb/gadget/function/u_serial.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 6f68cbe..af08a18 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -450,6 +450,15 @@ static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
 {
 	struct gs_port	*port = ep->driver_data;
 
+	/*
+	 * Port became NULL when 'dwc3_gadget_pullup' returns ETIMEDOUT.
+	 * Return here to avoid panic.
+	 */
+	if (!port) {
+		pr_err("%s, failed to get port\n", __func__);
+		return;
+	}
+
 	/* Queue all received data until the tty layer is ready for it. */
 	spin_lock(&port->port_lock);
 	list_add_tail(&req->list, &port->read_queue);
@@ -461,6 +470,15 @@ static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
 {
 	struct gs_port	*port = ep->driver_data;
 
+	/*
+	 * port became NULL when 'dwc3_gadget_pullup' returns ETIMEDOUT.
+	 * Return here to avoid panic.
+	 */
+	if (!port) {
+		pr_err("%s, failed to get port\n", __func__);
+		return;
+	}
+
 	spin_lock(&port->port_lock);
 	list_add(&req->list, &port->write_pool);
 	port->write_started--;
-- 
2.7.4