linux-kernel - [PATCH 2/2] usb: gadget: r8a66597: Fix a possible sleep-in-atomic-context bugs in r8a66597

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Message-Id: <20180620035509.7775-1-baijiaju1990@gmail.com>
Date:   Wed, 20 Jun 2018 11:55:08 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     balbi@...nel.org, gregkh@...uxfoundation.org, leoyang.li@....com,
        allen.lkml@...il.com, johan@...nel.org, keescook@...omium.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH 2/2] usb: gadget: r8a66597: Fix a possible sleep-in-atomic-context bugs in r8a66597_queue()

The driver may sleep in an interrupt handler.
The function call path (from bottom to top) in Linux-4.16.7 is:

[FUNC] r8a66597_queue(GFP_KERNEL)
drivers/usb/gadget/udc/r8a66597-udc.c, 1193: 
		r8a66597_queue in get_status
drivers/usb/gadget/udc/r8a66597-udc.c, 1301: 
		get_status in setup_packet
drivers/usb/gadget/udc/r8a66597-udc.c, 1381: 
		setup_packet in irq_control_stage
drivers/usb/gadget/udc/r8a66597-udc.c, 1508: 
		irq_control_stage in r8a66597_irq (interrupt handler)

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.

This bug is found by my static analysis tool (DSAC-2) and checked by
my code review.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/usb/gadget/udc/r8a66597-udc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/r8a66597-udc.c b/drivers/usb/gadget/udc/r8a66597-udc.c
index a3ecce62662b..e1292c280a0b 100644
--- a/drivers/usb/gadget/udc/r8a66597-udc.c
+++ b/drivers/usb/gadget/udc/r8a66597-udc.c
@@ -1190,7 +1190,7 @@ __acquires(r8a66597->lock)
 	r8a66597->ep0_req->length = 2;
 	/* AV: what happens if we get called again before that gets through? */
 	spin_unlock(&r8a66597->lock);
-	r8a66597_queue(r8a66597->gadget.ep0, r8a66597->ep0_req, GFP_KERNEL);
+	r8a66597_queue(r8a66597->gadget.ep0, r8a66597->ep0_req, GFP_ATOMIC);
 	spin_lock(&r8a66597->lock);
 }
 
-- 
2.17.0