CVE-2026-64366: HID: wacom: fix slab-out-of-bounds write in wacom_wac_queue_insert

From: Greg Kroah-Hartman <[email protected]>

Description
===========

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

HID: wacom: fix slab-out-of-bounds write in wacom_wac_queue_insert

wacom_wac_queue_insert() calls kfifo_skip() in a loop when the kfifo
doesn't have enough space for the incoming report. If the kfifo is
empty, kfifo_skip() reads stale data left in the kmalloc'd buffer
via __kfifo_peek_n() and interprets it as a record length, advancing
fifo->out by that garbage value. This corrupts the internal kfifo
state, causing kfifo_unused() to return a value much larger than the
actual buffer size, which bypasses __kfifo_in_r()'s guard:

  if (len + recsize > kfifo_unused(fifo))
      return 0;

kfifo_copy_in() then performs an out-of-bounds memcpy, writing up to
3842 bytes past the 256-byte buffer.

Add a !kfifo_is_empty() condition to the while loop so kfifo_skip()
is never called on an empty fifo, and check the return value of
kfifo_in() to reject reports that are too large for the fifo.

The Linux kernel CVE team has assigned CVE-2026-64366 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.15 with commit 5e013ad206895e72d7da41bc1ae89d8cb499c3aa and fixed in 6.18.39 with commit ca899a926c11a59211b764b0155d9a1cdcc32b81
	Issue introduced in 6.15 with commit 5e013ad206895e72d7da41bc1ae89d8cb499c3aa and fixed in 7.1.4 with commit 57bdd10ad50d68341f500a7b330f0d8949e510ec
	Issue introduced in 6.15 with commit 5e013ad206895e72d7da41bc1ae89d8cb499c3aa and fixed in 7.2-rc1 with commit 6b3014ec0e9a390ca563030b2d7689921f0daef5

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-64366
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/hid/wacom_sys.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/ca899a926c11a59211b764b0155d9a1cdcc32b81
	https://git.kernel.org/stable/c/57bdd10ad50d68341f500a7b330f0d8949e510ec
	https://git.kernel.org/stable/c/6b3014ec0e9a390ca563030b2d7689921f0daef5