Bryam Vargas 431ad239f2 Input: touchwin - reset the packet index on every complete packet
commit 478cdd736f upstream.

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:

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

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.

Fixes: 11ea3173d5 ("Input: add driver for Touchwin serial touchscreens")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Link: https://patch.msgid.link/20260613-b4-disp-69921bfd-v1-1-82c036899959@proton.me
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-07-24 16:02:55 +02:00
2026-05-23 13:03:09 +02:00
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2026-05-23 13:03:09 +02:00
2026-07-04 13:42:28 +02:00
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Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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