[PATCH v2 1/1] usb: misc: usbtest: add fix for driver hang

[Lu Baolu]

In sg_timeout(), req->status is set to "-ETIMEDOUT" before calling
into usb_sg_cancel(). usb_sg_cancel() will do nothing and return
directly if req->status has been set to a non-zero value. This will
cause driver hang whenever transfer time out is triggered.

This patch fixes this issue. It could be backported to stable kernel
with version later than v3.15.

Cc: stable@xxxxxxxxxxxxxxx # 3.15+
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 v1->v2:
 - Set retval to -ETIMEDOUT after timed out
 - Removed the kernel log in patch description

 drivers/usb/misc/usbtest.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/misc/usbtest.c b/drivers/usb/misc/usbtest.c
index 6b978f0..c273e11 100644
--- a/drivers/usb/misc/usbtest.c
+++ b/drivers/usb/misc/usbtest.c
@@ -585,7 +585,6 @@ static void sg_timeout(unsigned long _req)
 {
 	struct usb_sg_request	*req = (struct usb_sg_request *) _req;
 
-	req->status = -ETIMEDOUT;
 	usb_sg_cancel(req);
 }
 
@@ -616,8 +615,10 @@ static int perform_sglist(
 		mod_timer(&sg_timer, jiffies +
 				msecs_to_jiffies(SIMPLE_IO_TIMEOUT));
 		usb_sg_wait(req);
-		del_timer_sync(&sg_timer);
-		retval = req->status;
+		if (unlikely(!del_timer_sync(&sg_timer)))
+			retval = -ETIMEDOUT;
+		else
+			retval = req->status;
 
 		/* FIXME check resulting data pattern */
 
-- 
2.1.4