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    Subject[PATCH 3.10 159/250] USB: serial: digi_acceleport: fix OOB data sanity check
    Date
    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: Willy Tarreau <w@1wt.eu>
    ---
    drivers/usb/serial/digi_acceleport.c | 14 +++++++++-----
    1 file changed, 9 insertions(+), 5 deletions(-)

    diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
    index 8c34d9c..15b9cb3 100644
    --- a/drivers/usb/serial/digi_acceleport.c
    +++ b/drivers/usb/serial/digi_acceleport.c
    @@ -1489,16 +1489,20 @@ static int digi_read_oob_callback(struct urb *urb)
    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);
    --
    2.8.0.rc2.1.gbe9624a
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