[v2,3/5] usb: gadget: u_serial: Fix console_req access race

Commit Message

Ladislav Michl July 13, 2019, 9:11 p.m. UTC

console_req is always null when calling gs_console_connect, so
remove check and put access under con_lock as we are racing with
gs_console_thread.

Signed-off-by: Ladislav Michl <[e-mail]>
---
 Changes:
 - v2: New patch

 drivers/usb/gadget/function/u_serial.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

Patch

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index cb88a640179e..558a6929ce68 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -930,15 +930,12 @@  static int gs_console_connect(int port_num)
 
 	port = ports[port_num].port;
 	ep = port->port_usb->in;
-	if (!info->console_req) {
-		info->console_req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
-		if (!info->console_req)
-			return -ENOMEM;
-		info->console_req->complete = gs_complete_out;
-	}
-
-	info->port = port;
 	spin_lock(&info->con_lock);
+	info->console_req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
+	if (!info->console_req)
+		return -ENOMEM;
+	info->console_req->complete = gs_complete_out;
+	info->port = port;
 	info->req_busy = 0;
 	spin_unlock(&info->con_lock);
 	pr_vdebug("port[%d] console connect!\n", port_num);
@@ -948,10 +945,11 @@  static int gs_console_connect(int port_num)
 static void gs_console_disconnect(struct usb_ep *ep)
 {
 	struct gscons_info *info = &gscons_info;
-	struct usb_request *req = info->console_req;
 
-	gs_free_req(ep, req);
+	spin_lock(&info->con_lock);
+	gs_free_req(ep, info->console_req);
 	info->console_req = NULL;
+	spin_unlock(&info->con_lock);
 }
 
 static int gs_console_thread(void *data)
@@ -1008,7 +1006,6 @@  static int gs_console_setup(struct console *co, char *options)
 	info->port = NULL;
 	info->console_req = NULL;
 	info->req_busy = 0;
-	spin_lock_init(&info->con_lock);
 
 	status = kfifo_alloc(&info->con_buf, GS_CONSOLE_BUF_SIZE, GFP_KERNEL);
 	if (status) {
@@ -1064,6 +1061,9 @@  static struct console gserial_cons = {
 
 static void gserial_console_init(void)
 {
+	struct gscons_info *info = &gscons_info;
+
+	spin_lock_init(&info->con_lock);
 	register_console(&gserial_cons);
 }