---
id: CVE-2026-99179
title: 'watch_queue: Fix note pool publication race in watch_queue_set_size()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  watch_queue: Fix note pool publication race in watch_queue_set_size()

  There is a race between watch_queue_set_size() and post_one_notification().
  watch_queue_set_size(…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= c73be61cede5882f9605a852414db559c0ebedfd <
    811fb6d0b07605e8e8d93bde8748be4b3028809a
  - >-
    Linux >= c73be61cede5882f9605a852414db559c0ebedfd <
    9e73a6754457ffed8399b835552013b9363e51d1
  - >-
    Linux >= c73be61cede5882f9605a852414db559c0ebedfd <
    5e531d62f1f8834faf7a4eed0d41105cf6570a8f
  - Linux 5.8
published: '2026-10-28'
updated: '2026-10-28'
sourceUpdated: '2026-10-28T10:35:32.734Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99179'
references:
  - url: 'https://git.kernel.org/stable/c/811fb6d0b07605e8e8d93bde8748be4b3028809a'
  - url: 'https://git.kernel.org/stable/c/9e73a6754457ffed8399b835552013b9363e51d1'
  - url: 'https://git.kernel.org/stable/c/5e531d62f1f8834faf7a4eed0d41105cf6570a8f'
tags:
  - cve.org
ingestedAt: '2026-10-28T11:09:40.381Z'
---

## Overview

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

watch_queue: Fix note pool publication race in watch_queue_set_size()

There is a race between watch_queue_set_size() and post_one_notification().
watch_queue_set_size() publishes wqueue->notes, notes_bitmap, nr_pages and
nr_notes with plain stores, and post_one_notification() reads them with
plain loads under a different lock, so nothing orders the four stores
against the poster's loads: depending on the build, notes can be stored
last (gcc 14 on x86-64 does this).  Since keyctl_watch_key() lets a watch
attach to a queue before it is sized, post_one_notification() can already
be running on another CPU at that moment: it reads nr_notes > 0, passes
its bounds check, and then reads notes while it is still NULL,
dereferencing notes[0].

An unprivileged user triggers this reliably by watching one of its own
keys through a notification pipe and racing ioctl(IOC_WATCH_QUEUE_SET_SIZE)
on that pipe against keyctl(KEYCTL_SETPERM) on the key from another CPU,
triggering:

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  RIP: 0010:post_one_notification.isra.0+0xa2/0x1e0
  Call Trace:
   __post_watch_notification+0x148/0x180
   keyctl_setperm_key+0x119/0x130
   do_syscall_64+0x108/0x4c0
   entry_SYSCALL_64_after_hwframe+0x77/0x7f
  Kernel panic - not syncing: Fatal exception in interrupt

Fix this by publishing nr_notes last with smp_store_release(), and by
reading it once with smp_load_acquire() in post_one_notification() before
the bitmap and the page array are touched.  A poster that observes a
non-zero nr_notes then also observes the pool behind it; one that observes
zero drops the notification as before.

## Affected

- `Linux >= c73be61cede5882f9605a852414db559c0ebedfd < 811fb6d0b07605e8e8d93bde8748be4b3028809a`
- `Linux >= c73be61cede5882f9605a852414db559c0ebedfd < 9e73a6754457ffed8399b835552013b9363e51d1`
- `Linux >= c73be61cede5882f9605a852414db559c0ebedfd < 5e531d62f1f8834faf7a4eed0d41105cf6570a8f`
- `Linux 5.8`

## Remediation

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