linux-cve-announce - CVE-2025-38557: HID: apple: validate feature-report field count to prevent NULL pointer dereference

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Message-ID: <2025081905-CVE-2025-38557-4b79@gregkh>
Date: Tue, 19 Aug 2025 19:18:04 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38557: HID: apple: validate feature-report field count to prevent NULL pointer dereference

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

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

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

HID: apple: validate feature-report field count to prevent NULL pointer dereference

A malicious HID device with quirk APPLE_MAGIC_BACKLIGHT can trigger a NULL
pointer dereference whilst the power feature-report is toggled and sent to
the device in apple_magic_backlight_report_set(). The power feature-report
is expected to have two data fields, but if the descriptor declares one
field then accessing field[1] and dereferencing it in
apple_magic_backlight_report_set() becomes invalid
since field[1] will be NULL.

An example of a minimal descriptor which can cause the crash is something
like the following where the report with ID 3 (power report) only
references a single 1-byte field. When hid core parses the descriptor it
will encounter the final feature tag, allocate a hid_report (all members
of field[] will be zeroed out), create field structure and populate it,
increasing the maxfield to 1. The subsequent field[1] access and
dereference causes the crash.

  Usage Page (Vendor Defined 0xFF00)
  Usage (0x0F)
  Collection (Application)
    Report ID (1)
    Usage (0x01)
    Logical Minimum (0)
    Logical Maximum (255)
    Report Size (8)
    Report Count (1)
    Feature (Data,Var,Abs)

    Usage (0x02)
    Logical Maximum (32767)
    Report Size (16)
    Report Count (1)
    Feature (Data,Var,Abs)

    Report ID (3)
    Usage (0x03)
    Logical Minimum (0)
    Logical Maximum (1)
    Report Size (8)
    Report Count (1)
    Feature (Data,Var,Abs)
  End Collection

Here we see the KASAN splat when the kernel dereferences the
NULL pointer and crashes:

  [   15.164723] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP KASAN NOPTI
  [   15.165691] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
  [   15.165691] CPU: 0 UID: 0 PID: 10 Comm: kworker/0:1 Not tainted 6.15.0 #31 PREEMPT(voluntary)
  [   15.165691] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
  [   15.165691] RIP: 0010:apple_magic_backlight_report_set+0xbf/0x210
  [   15.165691] Call Trace:
  [   15.165691]  <TASK>
  [   15.165691]  apple_probe+0x571/0xa20
  [   15.165691]  hid_device_probe+0x2e2/0x6f0
  [   15.165691]  really_probe+0x1ca/0x5c0
  [   15.165691]  __driver_probe_device+0x24f/0x310
  [   15.165691]  driver_probe_device+0x4a/0xd0
  [   15.165691]  __device_attach_driver+0x169/0x220
  [   15.165691]  bus_for_each_drv+0x118/0x1b0
  [   15.165691]  __device_attach+0x1d5/0x380
  [   15.165691]  device_initial_probe+0x12/0x20
  [   15.165691]  bus_probe_device+0x13d/0x180
  [   15.165691]  device_add+0xd87/0x1510
  [...]

To fix this issue we should validate the number of fields that the
backlight and power reports have and if they do not have the required
number of fields then bail.

The Linux kernel CVE team has assigned CVE-2025-38557 to this issue.


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

	Issue introduced in 6.11 with commit 394ba612f9419ec5bfebbffb72212fd3b2094986 and fixed in 6.12.42 with commit ba08cc6801ec5fb98f2d02b5f0c614c931845325
	Issue introduced in 6.11 with commit 394ba612f9419ec5bfebbffb72212fd3b2094986 and fixed in 6.15.10 with commit 7e15d1eaa88179c5185e57a38ab05fe852d0cb8d
	Issue introduced in 6.11 with commit 394ba612f9419ec5bfebbffb72212fd3b2094986 and fixed in 6.16.1 with commit 00896c3f41cb6b74fec853386076115ba50baf0a
	Issue introduced in 6.11 with commit 394ba612f9419ec5bfebbffb72212fd3b2094986 and fixed in 6.17-rc1 with commit 1bb3363da862e0464ec050eea2fb5472a36ad86b

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-2025-38557
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/hid-apple.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/ba08cc6801ec5fb98f2d02b5f0c614c931845325
	https://git.kernel.org/stable/c/7e15d1eaa88179c5185e57a38ab05fe852d0cb8d
	https://git.kernel.org/stable/c/00896c3f41cb6b74fec853386076115ba50baf0a
	https://git.kernel.org/stable/c/1bb3363da862e0464ec050eea2fb5472a36ad86b