---
id: CVE-2026-52946
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling

  A SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in
  send_sigio() and send_sigurg() when a pro…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling

  A SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in
  send_sigio() and send_sigurg() when a pro…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-667
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.12.1, < 5.10.259'
  - 'linux_kernel >= 5.11, < 5.15.210'
  - 'linux_kernel >= 5.16, < 6.1.176'
  - 'linux_kernel >= 6.2, < 6.6.143'
  - 'linux_kernel >= 6.7, < 6.12.94'
  - 'linux_kernel >= 6.13, < 6.18.36'
  - 'linux_kernel >= 6.19, < 7.0.13'
  - 'linux_kernel >= 7.1, < 7.1.1'
  - linux_kernel = 2.6.12
patched:
  - linux_kernel 7.1.1
published: '2026-06-24'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T09:18:12.257'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52946'
references:
  - url: 'https://git.kernel.org/stable/c/00633c4683828acd5256fa8d5163f440d74bbe71'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1bee417678f1135e35b25a37734db46aa94258d2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/20a93e397abe850c49b6fa0e8cc827b5f634a8f5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/32dbd5ce4be3a3ed7e00f8af18795cc84fc50a33'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/36c1b57b2ecf3c61ac93f5f07bd29b6f21e226ed'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/54626335ea4174ab2d9a183b511d825f6765e47b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/897d6a7247739fb1528f98c575df4f2e5de7f994'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b5fa9e32fb6718f70c986ee14dd5d01b4846f331'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bfcc8e8d8a495bb34cae9e620adfb75fb13a3954'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00639
epssPercentile: 0.48352
ingestedAt: '2026-06-29T13:42:11.984Z'
---

## Overview

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

fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling

A SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in
send_sigio() and send_sigurg() when a process group receives a signal.

When FASYNC is configured for a process group (PIDTYPE_PGID), both
functions use read_lock(&tasklist_lock) to traverse the task list.
However, they are frequently called from softirq context:
- send_sigio() via input_inject_event -> kill_fasync
- send_sigurg() via tcp_check_urg -> sk_send_sigurg (NET_RX_SOFTIRQ)

The deadlock is caused by the rwlock writer fairness mechanism:
1. CPU 0 (process context) holds read_lock(&tasklist_lock) in do_wait().
2. CPU 1 (process context) attempts write_lock(&tasklist_lock) in
   fork() or exit() and spins, which blocks all new readers.
3. CPU 0 is interrupted by a softirq (e.g., TCP URG packet reception).
4. The softirq calls send_sigurg() and attempts to acquire
   read_lock(&tasklist_lock), deadlocking because CPU 1 is waiting.

Since PID hashing and do_each_pid_task() traversals are already
RCU-protected, the read_lock on tasklist_lock is no longer strictly
required for safe traversal. Fix this by replacing tasklist_lock with
rcu_read_lock(), aligning the process group signaling path with the
single-PID path. This also mitigates a potential remote denial of
service vector via TCP URG packets.

Lockdep splat:
=====================================================
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
[...]
Chain exists of:
  &dev->event_lock --> &f_owner->lock --> tasklist_lock

Possible interrupt unsafe locking scenario:
       CPU0                    CPU1
       ----                    ----
  lock(tasklist_lock);
                           local_irq_disable();
                           lock(&dev->event_lock);
                           lock(&f_owner->lock);
  <Interrupt>
    lock(&dev->event_lock);

*** DEADLOCK ***

## Affected

- `linux_kernel >= 2.6.12.1, < 5.10.259`
- `linux_kernel >= 5.11, < 5.15.210`
- `linux_kernel >= 5.16, < 6.1.176`
- `linux_kernel >= 6.2, < 6.6.143`
- `linux_kernel >= 6.7, < 6.12.94`
- `linux_kernel >= 6.13, < 6.18.36`
- `linux_kernel >= 6.19, < 7.0.13`
- `linux_kernel >= 7.1, < 7.1.1`
- `linux_kernel = 2.6.12`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.1.1`