linux-cve-announce - CVE-2025-68367: macintosh/mac_hid: fix race condition in mac_hid_toggle

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Message-ID: <2025122459-CVE-2025-68367-847e@gregkh>
Date: Wed, 24 Dec 2025 11:35:12 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68367: macintosh/mac_hid: fix race condition in mac_hid_toggle_emumouse

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

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

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

macintosh/mac_hid: fix race condition in mac_hid_toggle_emumouse

The following warning appears when running syzkaller, and this issue also
exists in the mainline code.

 ------------[ cut here ]------------
 list_add double add: new=ffffffffa57eee28, prev=ffffffffa57eee28, next=ffffffffa5e63100.
 WARNING: CPU: 0 PID: 1491 at lib/list_debug.c:35 __list_add_valid_or_report+0xf7/0x130
 Modules linked in:
 CPU: 0 PID: 1491 Comm: syz.1.28 Not tainted 6.6.0+ #3
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
 RIP: 0010:__list_add_valid_or_report+0xf7/0x130
 RSP: 0018:ff1100010dfb7b78 EFLAGS: 00010282
 RAX: 0000000000000000 RBX: ffffffffa57eee18 RCX: ffffffff97fc9817
 RDX: 0000000000040000 RSI: ffa0000002383000 RDI: 0000000000000001
 RBP: ffffffffa57eee28 R08: 0000000000000001 R09: ffe21c0021bf6f2c
 R10: 0000000000000001 R11: 6464615f7473696c R12: ffffffffa5e63100
 R13: ffffffffa57eee28 R14: ffffffffa57eee28 R15: ff1100010dfb7d48
 FS:  00007fb14398b640(0000) GS:ff11000119600000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 000000010d096005 CR4: 0000000000773ef0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 PKRU: 80000000
 Call Trace:
  <TASK>
  input_register_handler+0xb3/0x210
  mac_hid_start_emulation+0x1c5/0x290
  mac_hid_toggle_emumouse+0x20a/0x240
  proc_sys_call_handler+0x4c2/0x6e0
  new_sync_write+0x1b1/0x2d0
  vfs_write+0x709/0x950
  ksys_write+0x12a/0x250
  do_syscall_64+0x5a/0x110
  entry_SYSCALL_64_after_hwframe+0x78/0xe2

The WARNING occurs when two processes concurrently write to the mac-hid
emulation sysctl, causing a race condition in mac_hid_toggle_emumouse().
Both processes read old_val=0, then both try to register the input handler,
leading to a double list_add of the same handler.

  CPU0                             CPU1
  -------------------------        -------------------------
  vfs_write() //write 1            vfs_write()  //write 1
    proc_sys_write()                 proc_sys_write()
      mac_hid_toggle_emumouse()          mac_hid_toggle_emumouse()
        old_val = *valp // old_val=0
                                           old_val = *valp // old_val=0
                                           mutex_lock_killable()
                                           proc_dointvec() // *valp=1
                                           mac_hid_start_emulation()
                                             input_register_handler()
                                           mutex_unlock()
        mutex_lock_killable()
        proc_dointvec()
        mac_hid_start_emulation()
          input_register_handler() //Trigger Warning
        mutex_unlock()

Fix this by moving the old_val read inside the mutex lock region.

The Linux kernel CVE team has assigned CVE-2025-68367 to this issue.


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

	Issue introduced in 2.6.34 with commit 99b089c3c38a83ebaeb1cc4584ddcde841626467 and fixed in 6.12.63 with commit 230621ffdb361d15cd3ef92d8b4fa8d314f4fad4
	Issue introduced in 2.6.34 with commit 99b089c3c38a83ebaeb1cc4584ddcde841626467 and fixed in 6.17.13 with commit 388391dd1cc567fcf0b372b63d414c119d23e911
	Issue introduced in 2.6.34 with commit 99b089c3c38a83ebaeb1cc4584ddcde841626467 and fixed in 6.18.2 with commit 48a7d427eb65922b3f17fbe00e2bbc7cb9eac381
	Issue introduced in 2.6.34 with commit 99b089c3c38a83ebaeb1cc4584ddcde841626467 and fixed in 6.19-rc1 with commit 1e4b207ffe54cf33a4b7a2912c4110f89c73bf3f

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-2025-68367
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/macintosh/mac_hid.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/230621ffdb361d15cd3ef92d8b4fa8d314f4fad4
	https://git.kernel.org/stable/c/388391dd1cc567fcf0b372b63d414c119d23e911
	https://git.kernel.org/stable/c/48a7d427eb65922b3f17fbe00e2bbc7cb9eac381
	https://git.kernel.org/stable/c/1e4b207ffe54cf33a4b7a2912c4110f89c73bf3f