---
id: CVE-2026-99234
title: 'tracing: Unregister field variable histograms when the command fails'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  tracing: Unregister field variable histograms when the command fails

  An action that names a field on another event needs that field as a
  variable, so create_field_var_…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    f21351d1c4cdcc6a68f03636a407c2af1a5e1e10
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    dba0f492703956801149cc70b39d2650a37995c3
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    a3d7ffd2409700748a495b645948fef48199206e
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    aae0ccd7326eef78dcdefffef3d1253e6f0615ca
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    8482ec5b65f606d5bbcec518e0afc69ad65ca414
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    431959fc76456cbba539279fe8967aa9391e6f23
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    5afb9317e2eeb1c7021a82995ce244fda5a4bd4f
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    d0090baf02dd08f6e909f36f0ad54a4e80f5e79b
  - >-
    Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 <
    91c14d6c13096091c56304120aaa26e479130b8b
  - Linux 4.17
published: '2026-11-02'
updated: '2026-11-03'
sourceUpdated: '2026-11-03T19:13:02.797Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99234'
references:
  - url: 'https://git.kernel.org/stable/c/f21351d1c4cdcc6a68f03636a407c2af1a5e1e10'
  - url: 'https://git.kernel.org/stable/c/dba0f492703956801149cc70b39d2650a37995c3'
  - url: 'https://git.kernel.org/stable/c/a3d7ffd2409700748a495b645948fef48199206e'
  - url: 'https://git.kernel.org/stable/c/aae0ccd7326eef78dcdefffef3d1253e6f0615ca'
  - url: 'https://git.kernel.org/stable/c/8482ec5b65f606d5bbcec518e0afc69ad65ca414'
  - url: 'https://git.kernel.org/stable/c/431959fc76456cbba539279fe8967aa9391e6f23'
  - url: 'https://git.kernel.org/stable/c/5afb9317e2eeb1c7021a82995ce244fda5a4bd4f'
  - url: 'https://git.kernel.org/stable/c/d0090baf02dd08f6e909f36f0ad54a4e80f5e79b'
  - url: 'https://git.kernel.org/stable/c/91c14d6c13096091c56304120aaa26e479130b8b'
tags:
  - cve.org
epss: 0.00182
epssPercentile: 0.0786
ingestedAt: '2026-11-05T20:33:06.386Z'
---

## Overview

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

tracing: Unregister field variable histograms when the command fails

An action that names a field on another event needs that field as a
variable, so create_field_var_hist() registers a second hist trigger on
that event to provide it, and records it in
target_hist_data->field_var_hists[].

If a later part of the same command fails, create_actions() returns an
error and event_hist_trigger_parse() jumps to out_free. The write fails
with -EINVAL and sched_switch gets no trigger, but:

  # echo 'hist:keys=pid:ts0=common_timestamp.usecs' >> \
      events/sched/sched_waking/trigger
  # echo 'my_synth u64 lat; int a; int b' >> synthetic_events
  # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:\
      onmatch(sched.sched_waking).my_synth($wakeup_lat,prio,nosuchfld)'\
      >> events/sched/sched_switch/trigger
  # cat events/sched/sched_waking/trigger
  hist:keys=pid:vals=hitcount:ts0=common_timestamp.usecs:sort=hitcount:size=2048:clock=global [active]
  hist:keys=pid:vals=hitcount:synthetic_prio=prio:sort=hitcount:size=2048 [active]

The second histogram is the one created for 'prio'. It is still active and
still counting.

out_free reaches destroy_field_var_hists(), which frees the
field_var_hists[] entries, but never unregister_field_var_hists(), which is
what removes the triggers and runs only from event_hist_trigger_free(). The
entry is freed and the trigger is left with nothing tracking it.

Unregister the field variable histograms in out_free as well, and record
each one as soon as its trigger is registered rather than after the lookup
that follows it, so no exit can leave a registered trigger untracked. The
entry then belongs to field_var_hists[] and is released by
destroy_field_var_hists(), so freeing it on that exit would be a double
free.

## Affected

- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < f21351d1c4cdcc6a68f03636a407c2af1a5e1e10`
- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < dba0f492703956801149cc70b39d2650a37995c3`
- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < a3d7ffd2409700748a495b645948fef48199206e`
- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < aae0ccd7326eef78dcdefffef3d1253e6f0615ca`
- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < 8482ec5b65f606d5bbcec518e0afc69ad65ca414`
- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < 431959fc76456cbba539279fe8967aa9391e6f23`
- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < 5afb9317e2eeb1c7021a82995ce244fda5a4bd4f`
- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < d0090baf02dd08f6e909f36f0ad54a4e80f5e79b`
- `Linux >= 02205a6752f223779a1b0e9e8ffacbea6e717851 < 91c14d6c13096091c56304120aaa26e479130b8b`
- `Linux 4.17`

## Remediation

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