[PATCH 3.2 093/131] USB: serial: fix potential stack buffer overflow

[Ben Hutchings]

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

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

From: Johan Hovold <johan@xxxxxxxxxx>

commit d979e9f9ecab04c1ecca741370e30a8a498893f5 upstream.

Make sure to verify the maximum number of endpoints per type to avoid
writing beyond the end of a stack-allocated array.

The current usb-serial implementation is limited to eight ports per
interface but failed to verify that the number of endpoints of a certain
type reported by a device did not exceed this limit.

Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/usb/serial/usb-serial.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -791,29 +791,39 @@ int usb_serial_probe(struct usb_interfac
 		if (usb_endpoint_is_bulk_in(endpoint)) {
 			/* we found a bulk in endpoint */
 			dbg("found bulk in on endpoint %d", i);
-			bulk_in_endpoint[num_bulk_in] = endpoint;
-			++num_bulk_in;
+			if (num_bulk_in < MAX_NUM_PORTS) {
+				bulk_in_endpoint[num_bulk_in] = endpoint;
+				++num_bulk_in;
+			}
 		}
 
 		if (usb_endpoint_is_bulk_out(endpoint)) {
 			/* we found a bulk out endpoint */
 			dbg("found bulk out on endpoint %d", i);
-			bulk_out_endpoint[num_bulk_out] = endpoint;
-			++num_bulk_out;
+			if (num_bulk_out < MAX_NUM_PORTS) {
+				bulk_out_endpoint[num_bulk_out] = endpoint;
+				++num_bulk_out;
+			}
 		}
 
 		if (usb_endpoint_is_int_in(endpoint)) {
 			/* we found a interrupt in endpoint */
 			dbg("found interrupt in on endpoint %d", i);
-			interrupt_in_endpoint[num_interrupt_in] = endpoint;
-			++num_interrupt_in;
+			if (num_interrupt_in < MAX_NUM_PORTS) {
+				interrupt_in_endpoint[num_interrupt_in] =
+						endpoint;
+				++num_interrupt_in;
+			}
 		}
 
 		if (usb_endpoint_is_int_out(endpoint)) {
 			/* we found an interrupt out endpoint */
 			dbg("found interrupt out on endpoint %d", i);
-			interrupt_out_endpoint[num_interrupt_out] = endpoint;
-			++num_interrupt_out;
+			if (num_interrupt_out < MAX_NUM_PORTS) {
+				interrupt_out_endpoint[num_interrupt_out] =
+						endpoint;
+				++num_interrupt_out;
+			}
 		}
 	}
 
@@ -836,8 +846,10 @@ int usb_serial_probe(struct usb_interfac
 				if (usb_endpoint_is_int_in(endpoint)) {
 					/* we found a interrupt in endpoint */
 					dbg("found interrupt in for Prolific device on separate interface");
-					interrupt_in_endpoint[num_interrupt_in] = endpoint;
-					++num_interrupt_in;
+					if (num_interrupt_in < MAX_NUM_PORTS) {
+						interrupt_in_endpoint[num_interrupt_in] = endpoint;
+						++num_interrupt_in;
+					}
 				}
 			}
 		}

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