[PATCH 4.9 01/44] USB: serial: digi_acceleport: fix OOB data sanity check

Greg Kroah-Hartman
2017-03-16T14:33:04Z

From: Johan Hovold <johan@kernel.org>

commit 2d380889215fe20b8523345649dee0579821800c upstream.

Make sure to check for short transfers to avoid underflow in a loop
condition when parsing the receive buffer.

Also fix an off-by-one error in the incomplete sanity check which could
lead to invalid data being parsed.

Fixes: 8c209e6782ca ("USB: make actual_length in struct urb field u32")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/serial/digi_acceleport.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -1482,16 +1482,20 @@ static int digi_read_oob_callback(struct
struct usb_serial *serial = port->serial;
struct tty_struct *tty;
struct digi_port *priv = usb_get_serial_port_data(port);
+ unsigned char *buf = urb->transfer_buffer;
int opcode, line, status, val;
int i;
unsigned int rts;

+ if (urb->actual_length < 4)
+ return -1;
+
/* handle each oob command */
- for (i = 0; i < urb->actual_length - 3;) {
- opcode = ((unsigned char *)urb->transfer_buffer)[i++];
- line = ((unsigned char *)urb->transfer_buffer)[i++];
- status = ((unsigned char *)urb->transfer_buffer)[i++];
- val = ((unsigned char *)urb->transfer_buffer)[i++];
+ for (i = 0; i < urb->actual_length - 4; i += 4) {
+ opcode = buf[i];
+ line = buf[i + 1];
+ status = buf[i + 2];
+ val = buf[i + 3];

dev_dbg(&port->dev, "digi_read_oob_callback: opcode=%d, line=%d, status=%d, val=%d\n",
opcode, line, status, val);