Input: iforce - bound the device-reported force-feedback effect index

Input: iforce - bound the device-reported force-feedback effect index

iforce_process_packet() handles a status report (packet id 0x02) by
taking a force-feedback effect index straight from the device wire and
using it to address the per-effect state array:

	i = data[1] & 0x7f;
	if (data[1] & 0x80) {
		if (!test_and_set_bit(FF_CORE_IS_PLAYED,
				      iforce->core_effects[i].flags))
			...
	} else if (test_and_clear_bit(FF_CORE_IS_PLAYED,
				      iforce->core_effects[i].flags)) {
		...
	}

The index is masked only with 0x7f, so it ranges 0..127, but
core_effects[] holds only IFORCE_EFFECTS_MAX (32) entries.  For an index
of 32..127 the test_and_set_bit()/test_and_clear_bit() is an
out-of-bounds single-bit read-modify-write past the array.  core_effects[]
is the second-to-last member of struct iforce, so the write lands in the
trailing members and beyond the embedding kzalloc()'d iforce_serio /
iforce_usb object.

data[1] is unvalidated device payload on both transports (the USB
interrupt endpoint and serio), and the status path is not gated on force
feedback being present, so a malicious or counterfeit device can set or
clear a bit at an attacker-chosen offset past the object.

Reject an out-of-range index instead of indexing with it.  Bound against
the array dimension IFORCE_EFFECTS_MAX rather than dev->ff->max_effects so
the check guarantees memory safety regardless of how many effects the
device registered.  A legitimate "effect started/stopped" status always
carries an index below IFORCE_EFFECTS_MAX, so well-formed devices are
unaffected; the neighbouring mark_core_as_ready() loop is already bounded
and is left untouched.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260613-b4-disp-4828d263-v1-1-02320e1a89dd@proton.me
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>