[PATCH 3.16 305/328] usb: usbip: Fix BUG: KASAN: slab-out-of-bounds in vhci_hub_control()

[Ben Hutchings]

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

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

From: "Shuah Khan (Samsung OSG)" <shuah@xxxxxxxxxx>

commit 81f7567c51ad97668d1c3a48e8ecc482e64d4161 upstream.

vhci_hub_control() accesses port_status array with out of bounds port
value. Fix it to reference port_status[] only with a valid rhport value
when invalid_rhport flag is true.

The invalid_rhport flag is set early on after detecting in port value
is within the bounds or not.

The following is used reproduce the problem and verify the fix:
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14ed8ab6400000

Reported-by: syzbot+bccc1fe10b70fadc78d0@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16:
 - s/VHCI_HC_PORTS/VHCI_NPORTS/
 - Mask wIndex before using it, as done upstream in commit 1c9de5bf4286
   "usbip: vhci-hcd: Add USB3 SuperSpeed support"
 - Drop inapplicable changes
 - Adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/drivers/staging/usbip/vhci_hcd.c
+++ b/drivers/staging/usbip/vhci_hcd.c
@@ -234,7 +234,8 @@ static int vhci_hub_control(struct usb_h
 {
 	struct vhci_hcd	*dum;
 	int             retval = 0;
-	int		rhport;
+	int		rhport = -1;
+	bool invalid_rhport = false;
 
 	u32 prev_port_status[VHCI_NPORTS];
 
@@ -245,11 +246,23 @@ static int vhci_hub_control(struct usb_h
 	 * NOTE:
 	 * wIndex shows the port number and begins from 1.
 	 */
+	wIndex = ((__u8)(wIndex & 0x00ff));
 	usbip_dbg_vhci_rh("typeReq %x wValue %x wIndex %x\n", typeReq, wValue,
 			  wIndex);
-	if (wIndex > VHCI_NPORTS)
-		pr_err("invalid port number %d\n", wIndex);
-	rhport = ((__u8)(wIndex & 0x00ff)) - 1;
+
+	/*
+	 * wIndex can be 0 for some request types (typeReq). rhport is
+	 * in valid range when wIndex >= 1 and < VHCI_HC_PORTS.
+	 *
+	 * Reference port_status[] only with valid rhport when
+	 * invalid_rhport is false.
+	 */
+	if (wIndex < 1 || wIndex > VHCI_NPORTS) {
+		invalid_rhport = true;
+		if (wIndex > VHCI_NPORTS)
+			pr_err("invalid port number %d\n", wIndex);
+	} else
+		rhport = wIndex - 1;
 
 	dum = hcd_to_vhci(hcd);
 
@@ -257,8 +270,9 @@ static int vhci_hub_control(struct usb_h
 
 	/* store old status and compare now and old later */
 	if (usbip_dbg_flag_vhci_rh) {
-		memcpy(prev_port_status, dum->port_status,
-			sizeof(prev_port_status));
+		if (!invalid_rhport)
+			memcpy(prev_port_status, dum->port_status,
+				sizeof(prev_port_status));
 	}
 
 	switch (typeReq) {
@@ -266,8 +280,10 @@ static int vhci_hub_control(struct usb_h
 		usbip_dbg_vhci_rh(" ClearHubFeature\n");
 		break;
 	case ClearPortFeature:
-		if (rhport < 0)
+		if (invalid_rhport) {
+			pr_err("invalid port number %d\n", wIndex);
 			goto error;
+		}
 		switch (wValue) {
 		case USB_PORT_FEAT_SUSPEND:
 			if (dum->port_status[rhport] & USB_PORT_STAT_SUSPEND) {
@@ -315,9 +331,10 @@ static int vhci_hub_control(struct usb_h
 		break;
 	case GetPortStatus:
 		usbip_dbg_vhci_rh(" GetPortStatus port %x\n", wIndex);
-		if (wIndex > VHCI_NPORTS || wIndex < 1) {
+		if (invalid_rhport) {
 			pr_err("invalid port number %d\n", wIndex);
 			retval = -EPIPE;
+			goto error;
 		}
 
 		/* we do not care about resume. */
@@ -372,8 +389,10 @@ static int vhci_hub_control(struct usb_h
 		case USB_PORT_FEAT_RESET:
 			usbip_dbg_vhci_rh(
 				" SetPortFeature: USB_PORT_FEAT_RESET\n");
-			if (rhport < 0)
+			if (invalid_rhport) {
+				pr_err("invalid port number %d\n", wIndex);
 				goto error;
+			}
 			/* if it's already running, disconnect first */
 			if (dum->port_status[rhport] & USB_PORT_STAT_ENABLE) {
 				dum->port_status[rhport] &=
@@ -389,8 +408,10 @@ static int vhci_hub_control(struct usb_h
 		default:
 			usbip_dbg_vhci_rh(" SetPortFeature: default %d\n",
 					  wValue);
-			if (rhport < 0)
+			if (invalid_rhport) {
+				pr_err("invalid port number %d\n", wIndex);
 				goto error;
+			}
 			dum->port_status[rhport] |= (1 << wValue);
 			break;
 		}
@@ -406,7 +427,7 @@ error:
 	if (usbip_dbg_flag_vhci_rh) {
 		pr_debug("port %d\n", rhport);
 		/* Only dump valid port status */
-		if (rhport >= 0) {
+		if (!invalid_rhport) {
 			dump_port_status_diff(prev_port_status[rhport],
 					      dum->port_status[rhport]);
 		}