HID: wacom: validate report length in wacom_intuos_pro2_bt_irq

In the Linux kernel, the following vulnerability has been resolved:

HID: wacom: validate report length in wacom_intuos_pro2_bt_irq

wacom_intuos_pro2_bt_irq() receives the wire report length in `len`
but never consults it before parsing. After the report-id gate it
unconditionally calls wacom_intuos_pro2_bt_pen() and then, selected by
features.type, a fixed chain of sub-parsers, none of which receive
`len`:

wacom_intuos_pro2_bt_pen(wacom);
if (type == INTUOSP2_BT || type == INTUOSP2S_BT) {
wacom_intuos_pro2_bt_touch(wacom);
wacom_intuos_pro2_bt_pad(wacom);
wacom_intuos_pro2_bt_battery(wacom);
} else {
wacom_intuos_gen3_bt_pad(wacom);
wacom_intuos_gen3_bt_battery(wacom);
}

Each sub-parser dereferences wacom->data at fixed offsets. The furthest
byte touched on each branch is:

INTUOSP2_BT / INTUOSP2S_BT: wacom_intuos_pro2_bt_pad() reads data[285]
(the touchring byte), so the report must be at least 286 bytes;
INTUOSHT3_BT ("gen3"): wacom_intuos_gen3_bt_battery() reads data[45],
so the report must be at least 46 bytes.

features.type is selected from the VID/PID id_table entry and
wacom_setup_device_quirks() force-registers the pen/pad/touch inputs
for that type independent of the report descriptor, so a malicious or
malfunctioning paired/spoofed Bluetooth peripheral can advertise that
VID/PID and send an undersized report that still satisfies the
data[0] == 0x80/0x81 gate. The driver then reads past the received
report and forwards the bytes to userspace via evdev (MSC_SERIAL /
ABS_MISC / ABS_WHEEL on the pen and pad input nodes), an out-of-bounds
read with a concrete userspace read-back channel, and a true
out-of-bounds read on transports whose backing buffer is sized to the
(small) report descriptor rather than a fixed-size staging buffer.

This is the same class of bug commit 2f1763f62909 ("HID: wacom: fix
out-of-bounds read in wacom_intuos_bt_irq") already hardened in the
sibling wacom_intuos_bt_irq(), which guards each report id against its
minimum length before parsing.

Guard wacom_intuos_pro2_bt_irq() the same way: before parsing, reject
reports shorter than the furthest offset the selected branch actually
dereferences, warn, and bail out. Because the whole pen/touch/pad/
battery chain runs unconditionally per branch, a single up-front check
against the maximum offset (286 bytes for INTUOSP2_BT/INTUOSP2S_BT,
46 bytes for the gen3 branch) bounds every sub-parser. Returning 0 on
a short report also skips those calls for the same malformed report,
which is the safe, conservative behavior.