---
id: CVE-2025-38040
title: 'serial: mctrl_gpio: split disable_ms into sync and no_sync APIs'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  serial: mctrl_gpio: split disable_ms into sync and no_sync APIs

  The following splat has been observed on a SAMA5D27 platform using
  atmel_serial:

  BUG: sleeping functio…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 <
    68435c1fa3db696db4f480385db9e50e26691d0d
  - >-
    Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 <
    c504c11b94d6e4ad818ca5578dffa8ff29ad0f20
  - >-
    Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 <
    e6a46719a2369eb5186d4f7e6c0478720ca1ec3d
  - >-
    Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 <
    7187ec6b0b9ff22ebac2c3bb4178b7dbbdc0a55a
  - >-
    Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 <
    1bd2aad57da95f7f2d2bb52f7ad15c0f4993a685
  - Linux 4.4
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T20:48:34.069369Z'
published: '2025-06-18'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:52:13.449Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-38040'
references:
  - url: 'https://git.kernel.org/stable/c/68435c1fa3db696db4f480385db9e50e26691d0d'
  - url: 'https://git.kernel.org/stable/c/c504c11b94d6e4ad818ca5578dffa8ff29ad0f20'
  - url: 'https://git.kernel.org/stable/c/e6a46719a2369eb5186d4f7e6c0478720ca1ec3d'
  - url: 'https://git.kernel.org/stable/c/7187ec6b0b9ff22ebac2c3bb4178b7dbbdc0a55a'
  - url: 'https://git.kernel.org/stable/c/1bd2aad57da95f7f2d2bb52f7ad15c0f4993a685'
tags:
  - cve.org
epss: 0.00195
epssPercentile: 0.09289
ingestedAt: '2026-11-05T22:38:31.912Z'
---

## Overview

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

serial: mctrl_gpio: split disable_ms into sync and no_sync APIs

The following splat has been observed on a SAMA5D27 platform using
atmel_serial:

BUG: sleeping function called from invalid context at kernel/irq/manage.c:738
in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 27, name: kworker/u5:0
preempt_count: 1, expected: 0
INFO: lockdep is turned off.
irq event stamp: 0
hardirqs last  enabled at (0): [<00000000>] 0x0
hardirqs last disabled at (0): [<c01588f0>] copy_process+0x1c4c/0x7bec
softirqs last  enabled at (0): [<c0158944>] copy_process+0x1ca0/0x7bec
softirqs last disabled at (0): [<00000000>] 0x0
CPU: 0 UID: 0 PID: 27 Comm: kworker/u5:0 Not tainted 6.13.0-rc7+ #74
Hardware name: Atmel SAMA5
Workqueue: hci0 hci_power_on [bluetooth]
Call trace:
  unwind_backtrace from show_stack+0x18/0x1c
  show_stack from dump_stack_lvl+0x44/0x70
  dump_stack_lvl from __might_resched+0x38c/0x598
  __might_resched from disable_irq+0x1c/0x48
  disable_irq from mctrl_gpio_disable_ms+0x74/0xc0
  mctrl_gpio_disable_ms from atmel_disable_ms.part.0+0x80/0x1f4
  atmel_disable_ms.part.0 from atmel_set_termios+0x764/0x11e8
  atmel_set_termios from uart_change_line_settings+0x15c/0x994
  uart_change_line_settings from uart_set_termios+0x2b0/0x668
  uart_set_termios from tty_set_termios+0x600/0x8ec
  tty_set_termios from ttyport_set_flow_control+0x188/0x1e0
  ttyport_set_flow_control from wilc_setup+0xd0/0x524 [hci_wilc]
  wilc_setup [hci_wilc] from hci_dev_open_sync+0x330/0x203c [bluetooth]
  hci_dev_open_sync [bluetooth] from hci_dev_do_open+0x40/0xb0 [bluetooth]
  hci_dev_do_open [bluetooth] from hci_power_on+0x12c/0x664 [bluetooth]
  hci_power_on [bluetooth] from process_one_work+0x998/0x1a38
  process_one_work from worker_thread+0x6e0/0xfb4
  worker_thread from kthread+0x3d4/0x484
  kthread from ret_from_fork+0x14/0x28

This warning is emitted when trying to toggle, at the highest level,
some flow control (with serdev_device_set_flow_control) in a device
driver. At the lowest level, the atmel_serial driver is using
serial_mctrl_gpio lib to enable/disable the corresponding IRQs
accordingly.  The warning emitted by CONFIG_DEBUG_ATOMIC_SLEEP is due to
disable_irq (called in mctrl_gpio_disable_ms) being possibly called in
some atomic context (some tty drivers perform modem lines configuration
in regions protected by port lock).

Split mctrl_gpio_disable_ms into two differents APIs, a non-blocking one
and a blocking one. Replace mctrl_gpio_disable_ms calls with the
relevant version depending on whether the call is protected by some port
lock.

## Affected

- `Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 < 68435c1fa3db696db4f480385db9e50e26691d0d`
- `Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 < c504c11b94d6e4ad818ca5578dffa8ff29ad0f20`
- `Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 < e6a46719a2369eb5186d4f7e6c0478720ca1ec3d`
- `Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 < 7187ec6b0b9ff22ebac2c3bb4178b7dbbdc0a55a`
- `Linux >= ce59e48fdbad2aa6609ceb87e1306ec69e577e05 < 1bd2aad57da95f7f2d2bb52f7ad15c0f4993a685`
- `Linux 4.4`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.