[PATCH 5.5 153/170] USB: serial: io_edgeport: fix slab-out-of-bounds read in edge_interrupt_callback

[Greg Kroah-Hartman]

From: Qiujun Huang <hqjagain@xxxxxxxxx>

commit 57aa9f294b09463492f604feaa5cc719beaace32 upstream.

Fix slab-out-of-bounds read in the interrupt-URB completion handler.

The boundary condition should be (length - 1) as we access
data[position + 1].

Reported-and-tested-by: syzbot+37ba33391ad5f3935bbd@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Qiujun Huang <hqjagain@xxxxxxxxx>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/serial/io_edgeport.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -710,7 +710,7 @@ static void edge_interrupt_callback(stru
 		/* grab the txcredits for the ports if available */
 		position = 2;
 		portNumber = 0;
-		while ((position < length) &&
+		while ((position < length - 1) &&
 				(portNumber < edge_serial->serial->num_ports)) {
 			txCredits = data[position] | (data[position+1] << 8);
 			if (txCredits) {