CVE-2026-93050: ipack: ipoctal: fix UAF, null-ptr-deref, and use-after-free in cleanup on remove

CVE-2026-93050: ipack: ipoctal: fix UAF, null-ptr-deref, and use-after-free in cleanup on remove

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

ipack: ipoctal: fix UAF, null-ptr-deref, and use-after-free in cleanup on remove

Three issues arise when the device is removed while a tty session is
still active:

1. UAF of struct ipoctal: the remove callback frees ipoctal via
   kfree() while tty ops may still access it.  Fix by introducing
   kref-based lifetime management — kref is taken in install() when
   a tty is opened and released in cleanup() when the tty is finally
   destroyed; remove() uses kref_put() instead of kfree().

2. NULL dereference in ipoctal_write_tty(): __ipoctal_remove()
   frees xmit_buf via tty_port_free_xmit_buf() while a userspace
   process may still hold the tty fd and call write().  Fix by
   checking for NULL xmit_buf in ipoctal_write_tty().

3. UAF in ipoctal_cleanup(): ipack_put_carrier(ipoctal->dev)
   dereferences ipoctal->dev after the ipack_device has been freed
   by ipack_device_del().  Fix by caching ipoctal->carrier_owner
   during probe() and calling module_put() on the cached pointer
   directly in cleanup(), avoiding any access to ipoctal->dev.

Also introduce a "removed" flag in struct ipoctal, set at the start
of __ipoctal_remove(), and checked in every tty op that accesses
hardware resources (port_activate, write_tty, set_termios, hangup,
shutdown).  This prevents page faults when devm_ioremap() regions
are unmapped after remove() returns.

The Linux kernel CVE team has assigned CVE-2026-93050 to this issue.


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

	Issue introduced in 3.8 with commit 05e5027efc9c0bb6d1d04cde279afbafca0a7929 and fixed in 6.1.188 with commit ab5f5b27a340004b92252c6a5f23bf1c6cf3b02a
	Issue introduced in 3.8 with commit 05e5027efc9c0bb6d1d04cde279afbafca0a7929 and fixed in 6.6.157 with commit c92ef8fd834521f0b788e0511976c689fe57c63c
	Issue introduced in 3.8 with commit 05e5027efc9c0bb6d1d04cde279afbafca0a7929 and fixed in 6.12.110 with commit a4613140f01bd0fb9980e2746ed9aaa65a29b5d6
	Issue introduced in 3.8 with commit 05e5027efc9c0bb6d1d04cde279afbafca0a7929 and fixed in 6.18.52 with commit 1a3258e105f711538201bdd2ac2a05b11554eabc
	Issue introduced in 3.8 with commit 05e5027efc9c0bb6d1d04cde279afbafca0a7929 and fixed in 7.2.6 with commit 4a6518be316029650301f2a5e8f0def229b895d9
	Issue introduced in 3.8 with commit 05e5027efc9c0bb6d1d04cde279afbafca0a7929 and fixed in 7.3-rc1 with commit b6b5d64cb161a28347d64dc3168a636c4abb68d5

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-2026-93050
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/ipack/devices/ipoctal.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/ab5f5b27a340004b92252c6a5f23bf1c6cf3b02a
	https://git.kernel.org/stable/c/c92ef8fd834521f0b788e0511976c689fe57c63c
	https://git.kernel.org/stable/c/a4613140f01bd0fb9980e2746ed9aaa65a29b5d6
	https://git.kernel.org/stable/c/1a3258e105f711538201bdd2ac2a05b11554eabc
	https://git.kernel.org/stable/c/4a6518be316029650301f2a5e8f0def229b895d9
	https://git.kernel.org/stable/c/b6b5d64cb161a28347d64dc3168a636c4abb68d5