USB: serial: io_ti: fix information leak in completion handler

Add missing sanity check to the bulk-in completion handler to avoid an
integer underflow that can be triggered by a malicious device.

This avoids leaking 128 kB of memory content from after the URB transfer
buffer to user space.

Fixes: 8c209e6782ca ("USB: make actual_length in struct urb field u32")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>	# 2.6.30
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index 4561dd4..a76b95d 100644 (file)
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -1761,7 +1761,7 @@ static void edge_bulk_in_callback(struct urb *urb)
 
        port_number = edge_port->port->port_number;
 
-       if (edge_port->lsr_event) {
+       if (urb->actual_length > 0 && edge_port->lsr_event) {
                edge_port->lsr_event = 0;
                dev_dbg(dev, "%s ===== Port %u LSR Status = %02x, Data = %02x ======\n",
                        __func__, port_number, edge_port->lsr_mask, *data);