net: usb: kalmia: bound RX frame length in kalmia_rx_fixup()

In the Linux kernel, the following vulnerability has been resolved: net: usb: kalmia: bound RX frame length in kalmia_rx_fixup() kalmia_rx_fixup() computes usb_packet_length = skb->len - (2 * KALMIA_HEADER_LENGTH) as a u16, guarded only by a pre-loop check that skb->len is at least KALMIA_HEADER_LENGTH, which is 6. A device can deliver a short bulk-IN frame with skb->len in the 6 to 11 range, or leave a short trailing remainder on a later loop iteration. Either case underflows usb_packet_length to about 65530. That bypasses the usb_packet_length < ether_packet_length truncation path. The device-supplied ether_packet_length, a le16 up to 65535 read from header_start[2], then drives a memcmp() and the following skb_trim() and skb_pull() past the end of the rx buffer. The rx buffer is hard_mtu * 10, which is 14000 bytes. That is an out of bounds read. Require both the start and end framing headers to be present before subtracting them, on every loop iteration.