In the Linux kernel, the following vulnerability has been resolved:
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:
<pre>
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)) {
...
}
</pre>
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.