In the Linux kernel, the following vulnerability has been resolved: Input: touchwin - reset the packet index on every complete packet tw_i

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

Input: touchwin - reset the packet index on every complete packet

tw_interrupt() accumulates each non-zero serial byte into a fixed
three-byte buffer with a running index that is only reset once a full
packet has been received and the device's two Y bytes agree:

 1tw->data[tw->idx++] = data;
 2if (tw->idx == TW_LENGTH && tw->data[1] == tw->data[2]) {
 3	...
 4	tw->idx = 0;
 5}

The reset is gated on tw->data[1] == tw->data[2], a value the device
controls. A malicious, malfunctioning or counterfeit Touchwindow
peripheral can stream non-zero bytes whose 2nd and 3rd bytes differ: the
index reaches TW_LENGTH without the equality holding, is never reset, and
keeps growing, so tw->data[tw->idx++] walks off the end of the three-byte
array and the rest of the heap-allocated struct tw, one attacker-chosen
byte at a time -- an unbounded, device-driven heap out-of-bounds write.

Reset the index on every completed packet and report an event only when
the two Y bytes match, like the other serio touchscreen drivers do.