linux-kernel - Re: Re: UBSAN: shift-out-of-bounds in dummy_hub

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Date:   Tue, 29 Dec 2020 11:43:14 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     syzbot <syzbot+5925509f78293baa7331@...kaller.appspotmail.com>
Cc:     andreyknvl@...il.com, andreyknvl@...gle.com, balbi@...nel.org,
        gregkh@...uxfoundation.org, gustavoars@...nel.org,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: Re: UBSAN: shift-out-of-bounds in dummy_hub_control

On Tue, Dec 29, 2020 at 08:33:39AM -0800, syzbot wrote:
> > #syz test: upstream e37b12e4
>
> "upstream" does not look like a valid git repo address.

I thought syzbot had been changed to recognize "upstream" as a valid
repo name.

Alan Stern

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e37b12e4

Index: usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
===================================================================
--- usb-devel.orig/drivers/usb/gadget/udc/dummy_hcd.c
+++ usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
@@ -2114,9 +2114,21 @@ static int dummy_hub_control(
 				dum_hcd->port_status &= ~USB_PORT_STAT_POWER;
 			set_link_state(dum_hcd);
 			break;
-		default:
+		case USB_PORT_FEAT_ENABLE:
+		case USB_PORT_FEAT_C_ENABLE:
+		case USB_PORT_FEAT_C_SUSPEND:
+			/* Not allowed for USB-3 */
+			if (hcd->speed == HCD_USB3)
+				goto error;
+			fallthrough;
+		case USB_PORT_FEAT_C_CONNECTION:
+		case USB_PORT_FEAT_C_RESET:
 			dum_hcd->port_status &= ~(1 << wValue);
 			set_link_state(dum_hcd);
+			break;
+		default:
+		/* Disallow INDICATOR and C_OVER_CURRENT */
+			goto error;
 		}
 		break;
 	case GetHubDescriptor:
@@ -2277,18 +2289,17 @@ static int dummy_hub_control(
 			 */
 			dum_hcd->re_timeout = jiffies + msecs_to_jiffies(50);
 			fallthrough;
+		case USB_PORT_FEAT_C_CONNECTION:
+		case USB_PORT_FEAT_C_RESET:
+		case USB_PORT_FEAT_C_ENABLE:
+		case USB_PORT_FEAT_C_SUSPEND:
+			/* Not allowed for USB-3, and ignored for USB-2 */
+			if (hcd->speed == HCD_USB3)
+				goto error;
+			break;
 		default:
-			if (hcd->speed == HCD_USB3) {
-				if ((dum_hcd->port_status &
-				     USB_SS_PORT_STAT_POWER) != 0) {
-					dum_hcd->port_status |= (1 << wValue);
-				}
-			} else
-				if ((dum_hcd->port_status &
-				     USB_PORT_STAT_POWER) != 0) {
-					dum_hcd->port_status |= (1 << wValue);
-				}
-			set_link_state(dum_hcd);
+		/* Disallow TEST, INDICATOR, and C_OVER_CURRENT */
+			goto error;
 		}
 		break;
 	case GetPortErrorCount: