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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH 4.9 067/111] usb: cdc-wdm: Fix a sleep-in-atomic-context bug in service_outstanding_interrupt()
Date:   Mon, 24 Sep 2018 13:52:34 +0200
Message-Id: <20180924113111.668558851@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Jia-Ju Bai <baijiaju1990@gmail.com>

commit 6e22e3af7bb3a7b9dc53cb4687659f6e63fca427 upstream.

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@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/class/cdc-wdm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -470,7 +470,7 @@ static int service_outstanding_interrupt
 
 	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,