cve/published/2024/CVE-2024-36899.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2024-36899: gpiolib: cdev: Fix use after free in lineinfo_changed_notify

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

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

gpiolib: cdev: Fix use after free in lineinfo_changed_notify

The use-after-free issue occurs as follows: when the GPIO chip device file
is being closed by invoking gpio_chrdev_release(), watched_lines is freed
by bitmap_free(), but the unregistration of lineinfo_changed_nb notifier
chain failed due to waiting write rwsem. Additionally, one of the GPIO
chip's lines is also in the release process and holds the notifier chain's
read rwsem. Consequently, a race condition leads to the use-after-free of
watched_lines.

Here is the typical stack when issue happened:

[free]
gpio_chrdev_release()
  --> bitmap_free(cdev->watched_lines)                  <-- freed
  --> blocking_notifier_chain_unregister()
    --> down_write(&nh->rwsem)                          <-- waiting rwsem
          --> __down_write_common()
            --> rwsem_down_write_slowpath()
                  --> schedule_preempt_disabled()
                    --> schedule()

[use]
st54spi_gpio_dev_release()
  --> gpio_free()
    --> gpiod_free()
      --> gpiod_free_commit()
        --> gpiod_line_state_notify()
          --> blocking_notifier_call_chain()
            --> down_read(&nh->rwsem);                  <-- held rwsem
            --> notifier_call_chain()
              --> lineinfo_changed_notify()
                --> test_bit(xxxx, cdev->watched_lines) <-- use after free

The side effect of the use-after-free issue is that a GPIO line event is
being generated for userspace where it shouldn't. However, since the chrdev
is being closed, userspace won't have the chance to read that event anyway.

To fix the issue, call the bitmap_free() function after the unregistration
of lineinfo_changed_nb notifier chain.

The Linux kernel CVE team has assigned CVE-2024-36899 to this issue.


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

	Issue introduced in 5.7 with commit 51c1064e82e77b39a49889287ca50709303e2f26 and fixed in 5.10.234 with commit 2dfbb920a89bdc58087672ad5325dc6c588b6860
	Issue introduced in 5.7 with commit 51c1064e82e77b39a49889287ca50709303e2f26 and fixed in 5.15.177 with commit 2d008d4961b039d2edce8976289773961b7e5fb5
	Issue introduced in 5.7 with commit 51c1064e82e77b39a49889287ca50709303e2f26 and fixed in 6.1.127 with commit d38c49f7bdf14381270736299e2ff68ec248a017
	Issue introduced in 5.7 with commit 51c1064e82e77b39a49889287ca50709303e2f26 and fixed in 6.6.31 with commit 95ca7c90eaf5ea8a8460536535101e3e81160e2a
	Issue introduced in 5.7 with commit 51c1064e82e77b39a49889287ca50709303e2f26 and fixed in 6.8.10 with commit ca710b5f40b8b16fdcad50bebd47f50e4c62d239
	Issue introduced in 5.7 with commit 51c1064e82e77b39a49889287ca50709303e2f26 and fixed in 6.9 with commit 02f6b0e1ec7e0e7d059dddc893645816552039da

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-2024-36899
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/gpio/gpiolib-cdev.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/2dfbb920a89bdc58087672ad5325dc6c588b6860
	https://git.kernel.org/stable/c/2d008d4961b039d2edce8976289773961b7e5fb5
	https://git.kernel.org/stable/c/d38c49f7bdf14381270736299e2ff68ec248a017
	https://git.kernel.org/stable/c/95ca7c90eaf5ea8a8460536535101e3e81160e2a
	https://git.kernel.org/stable/c/ca710b5f40b8b16fdcad50bebd47f50e4c62d239
	https://git.kernel.org/stable/c/02f6b0e1ec7e0e7d059dddc893645816552039da