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.
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.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Mon, 02 Nov 2026 18:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Linux linux
|
|
| Vendors & Products |
Linux linux
|
Mon, 02 Nov 2026 16:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | tracing: Unregister field variable histograms when the command fails | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-11-02T16:06:41.083Z
Reserved: 2026-09-25T10:25:14.402Z
Link: CVE-2026-99234
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-11-02T16:17:48.597
Modified: 2026-11-02T16:17:48.597
Link: CVE-2026-99234
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-11-02T18:15:14Z
Weaknesses
No weakness.