usb: usbip: validate iso frame actual_length in usbip_recv_iso()

usb: usbip: validate iso frame actual_length in usbip_recv_iso()

usbip_recv_iso() sums each frame's actual_length into an int
accumulator without checking the individual values first:

    total_length += urb->iso_frame_desc[i].actual_length;

A malicious server can send actual_length = 0xFFFFFFFC for one frame
and a small value for the other, making the signed sum wrap around to
match urb->actual_length.  The sanity check passes, and usbip_pad_iso()
later computes a negative actualoffset, feeding it to memmove() as a
source pointer - reads before the allocation, leaked to userspace via
USBDEVFS_REAPURB.

Reject any frame whose actual_length exceeds transfer_buffer_length
(one frame can't carry more data than the whole buffer), and widen the
accumulator to u32 so that many moderately-large frames can't wrap it
either.

Signed-off-by: Kelvin Mbogo <addcontent08@gmail.com>
Link: https://patch.msgid.link/20260325103640.8090-2-addcontent08@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>