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Date:   Thu, 23 Apr 2020 12:37:05 -0400 (EDT)
From:   Alan Stern <stern@rowland.harvard.edu>
To:     syzbot <syzbot+db339689b2101f6f6071@syzkaller.appspotmail.com>
cc:     andreyknvl@google.com, <gregkh@linuxfoundation.org>,
        <ingrassia@epigenesys.com>, <linux-kernel@vger.kernel.org>,
        <linux-usb@vger.kernel.org>, <syzkaller-bugs@googlegroups.com>
Subject: Re: WARNING in usbhid_raw_request/usb_submit_urb (3)
In-Reply-To: <00000000000099a4f005a3eb458b@google.com>
Message-ID: <Pine.LNX.4.44L0.2004231235560.20147-100000@netrider.rowland.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, 22 Apr 2020, syzbot wrote:

> Hello,
> 
> syzbot has tested the proposed patch but the reproducer still triggered crash:
> WARNING in usbhid_raw_request/usb_submit_urb
> 
> usb 5-1: Ep 0 disabled: 2 0

This means that URB submission raced with usb_ep0_reinit().  Let's try 
to find out how.

Alan Stern

#syz test: https://github.com/google/kasan.git 0fa84af8

Index: usb-devel/drivers/usb/core/hub.c
===================================================================
--- usb-devel.orig/drivers/usb/core/hub.c
+++ usb-devel/drivers/usb/core/hub.c
@@ -4440,6 +4440,7 @@ void usb_ep0_reinit(struct usb_device *u
 	usb_disable_endpoint(udev, 0 + USB_DIR_IN, true);
 	usb_disable_endpoint(udev, 0 + USB_DIR_OUT, true);
 	usb_enable_endpoint(udev, &udev->ep0, true);
+	udev->alan1 = 0;
 }
 EXPORT_SYMBOL_GPL(usb_ep0_reinit);
 
@@ -4471,6 +4472,7 @@ static int hub_set_address(struct usb_de
 		update_devnum(udev, devnum);
 		/* Device now using proper address. */
 		usb_set_device_state(udev, USB_STATE_ADDRESS);
+		udev->alan1 = 1;
 		usb_ep0_reinit(udev);
 	}
 	return retval;
@@ -4838,6 +4840,7 @@ hub_port_init(struct usb_hub *hub, struc
 		else
 			dev_warn(&udev->dev, "Using ep0 maxpacket: %d\n", i);
 		udev->ep0.desc.wMaxPacketSize = cpu_to_le16(i);
+		udev->alan1 = 2;
 		usb_ep0_reinit(udev);
 	}
 
@@ -5226,6 +5229,7 @@ static void hub_port_connect(struct usb_
 loop_disable:
 		hub_port_disable(hub, port1, 1);
 loop:
+		udev->alan1 = 3;
 		usb_ep0_reinit(udev);
 		release_devnum(udev);
 		hub_free_dev(udev);
@@ -5766,6 +5770,7 @@ static int usb_reset_and_verify_device(s
 
 		/* ep0 maxpacket size may change; let the HCD know about it.
 		 * Other endpoints will be handled by re-enumeration. */
+		udev->alan1 = 4;
 		usb_ep0_reinit(udev);
 		ret = hub_port_init(parent_hub, udev, port1, i);
 		if (ret >= 0 || ret == -ENOTCONN || ret == -ENODEV)
Index: usb-devel/drivers/usb/core/urb.c
===================================================================
--- usb-devel.orig/drivers/usb/core/urb.c
+++ usb-devel/drivers/usb/core/urb.c
@@ -204,8 +204,12 @@ int usb_urb_ep_type_check(const struct u
 	const struct usb_host_endpoint *ep;
 
 	ep = usb_pipe_endpoint(urb->dev, urb->pipe);
-	if (!ep)
+	if (!ep) {
+		dev_info(&urb->dev->dev, "Ep %d disabled: %d\n",
+			usb_pipeendpoint(urb->pipe),
+			urb->dev->alan1);
 		return -EINVAL;
+	}
 	if (usb_pipetype(urb->pipe) != pipetypes[usb_endpoint_type(&ep->desc)])
 		return -EINVAL;
 	return 0;
Index: usb-devel/include/linux/usb.h
===================================================================
--- usb-devel.orig/include/linux/usb.h
+++ usb-devel/include/linux/usb.h
@@ -629,6 +629,7 @@ struct usb3_lpm_parameters {
  * usb_set_device_state().
  */
 struct usb_device {
+	int		alan1;
 	int		devnum;
 	char		devpath[16];
 	u32		route;