linux-kernel - [PATCH] usb: gadget: udc: fotg210-udc: Fix a sleep-in-atomic-context bug in fotg210_get

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Date:   Sat, 15 Sep 2018 11:04:40 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     balbi@...nel.org, gregkh@...uxfoundation.org,
        nicolas.ferre@...rochip.com, leoyang.li@....com,
        robert.jarzmik@...e.fr
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] usb: gadget: udc: fotg210-udc: Fix a sleep-in-atomic-context bug in fotg210_get_status()

The driver may sleep in an interrupt handler.
The function call path (from bottom to top) in Linux-4.17 is:

[FUNC] fotg210_ep_queue(GFP_KERNEL)
drivers/usb/gadget/udc/fotg210-udc.c, 744: 
	fotg210_ep_queue in fotg210_get_status
drivers/usb/gadget/udc/fotg210-udc.c, 768: 
	fotg210_get_status in fotg210_setup_packet
drivers/usb/gadget/udc/fotg210-udc.c, 949: 
	fotg210_setup_packet in fotg210_irq (interrupt handler)

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.
If possible, spin_unlock() and spin_lock() around fotg210_ep_queue() 
can be also removed.

This bug is found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/usb/gadget/udc/fotg210-udc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/fotg210-udc.c b/drivers/usb/gadget/udc/fotg210-udc.c
index 53a48f561458..c51510803d1f 100644
--- a/drivers/usb/gadget/udc/fotg210-udc.c
+++ b/drivers/usb/gadget/udc/fotg210-udc.c
@@ -741,7 +741,7 @@ static void fotg210_get_status(struct fotg210_udc *fotg210,
 	fotg210->ep0_req->length = 2;
 
 	spin_unlock(&fotg210->lock);
-	fotg210_ep_queue(fotg210->gadget.ep0, fotg210->ep0_req, GFP_KERNEL);
+	fotg210_ep_queue(fotg210->gadget.ep0, fotg210->ep0_req, GFP_ATOMIC);
 	spin_lock(&fotg210->lock);
 }
 
-- 
2.17.0