USB: cdc-acm: more sanity checking

oneukum · gregkh · commit 8835ba4a39cf · 2016-03-18T09:19:02.000-07:00
An attack has become available which pretends to be a quirky
device circumventing normal sanity checks and crashes the kernel
by an insufficient number of interfaces. This patch adds a check
to the code path for quirky devices.

Signed-off-by: Oliver Neukum &lt;ONeukum@suse.com&gt;
CC: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
@@ -1179,6 +1179,9 @@ static int acm_probe(struct usb_interface *intf,
 	if (quirks == NO_UNION_NORMAL) {
 		data_interface = usb_ifnum_to_if(usb_dev, 1);
 		control_interface = usb_ifnum_to_if(usb_dev, 0);
+		/* we would crash */
+		if (!data_interface || !control_interface)
+			return -ENODEV;
 		goto skip_normal_probe;
 	}
 

Original file line number	Diff line number	Diff line change
`@@ -1179,6 +1179,9 @@ static int acm_probe(struct usb_interface *intf,`
`1179`	`1179`	`if (quirks == NO_UNION_NORMAL) {`
`1180`	`1180`	`data_interface = usb_ifnum_to_if(usb_dev, 1);`
`1181`	`1181`	`control_interface = usb_ifnum_to_if(usb_dev, 0);`
	`1182`	`+ /* we would crash */`
	`1183`	`+ if (!data_interface \|\| !control_interface)`
	`1184`	`+ return -ENODEV;`
`1182`	`1185`	`goto skip_normal_probe;`
`1183`	`1186`	`}`
`1184`	`1187`