linux-kernel - [PATCH v2] usb: cdc-wdm: Fix a sleep-in-atomic-context bug in service_outstanding

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Date:   Sat,  1 Sep 2018 16:12:10 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     gregkh@...uxfoundation.org, johan@...nel.org, bjorn@...k.no,
        mingo@...nel.org, oneukum@...e.com, viro@...iv.linux.org.uk,
        mark.rutland@....com
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH v2] usb: cdc-wdm: Fix a sleep-in-atomic-context bug in service_outstanding_interrupt()

wdm_in_callback() is a completion handler function for the USB driver.
So it should not sleep. But it calls service_outstanding_interrupt(), 
which calls usb_submit_urb() with GFP_KERNEL. 

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.

This bug is found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
v2:
 * Add more description.
---
 drivers/usb/class/cdc-wdm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index a0d284ef3f40..632a2bfabc08 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -458,7 +458,7 @@ static int service_outstanding_interrupt(struct wdm_device *desc)
 
 	set_bit(WDM_RESPONDING, &desc->flags);
 	spin_unlock_irq(&desc->iuspin);
-	rv = usb_submit_urb(desc->response, GFP_KERNEL);
+	rv = usb_submit_urb(desc->response, GFP_ATOMIC);
 	spin_lock_irq(&desc->iuspin);
 	if (rv) {
 		dev_err(&desc->intf->dev,
-- 
2.17.0