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

commit 654b404f2a222f918af9b0cd18ad469d0c941a8e upstream.

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")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index 4874973..0fc2da9 100644 (file)
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -1766,7 +1766,7 @@ static void edge_bulk_in_callback(struct urb *urb)
 
        port_number = edge_port->port->number - edge_port->port->serial->minor;
 
-       if (edge_port->lsr_event) {
+       if (urb->actual_length > 0 && edge_port->lsr_event) {
                edge_port->lsr_event = 0;
                dbg("%s ===== Port %u LSR Status = %02x, Data = %02x ======",
                     __func__, port_number, edge_port->lsr_mask, *data);