CVE-2026-99140
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: tracing: Fix hist trigger timestamps for buffered events Syzkaller triggered a WARN_ON_ONCE(!nest) warning: WARNING: kernel/trace/ring_buffer.c:821 at ring_buffer_event_time_stamp Call trace: ring_buffer_event_time_stamp hist_field_timestamp hist_fn_call event_hist_trigger event_triggers_call __event_trigger_test_discard trace_event_buffer_commit do_trace_event_raw_event_sched_switch trace_event_raw_event_sched_switch The warning is probabilistically reproducible and is related to syzkaller executing the following commands: echo 'prev_pid == 999999' > events/sched/sched_switch/filter echo 'hist:keys=common_timestamp' > events/sched/sched_switch/trigger The specific triggering process is as follows: CPU 0 CPU 1 (context switching) (echo 'hist:keys=common_timestamp' > \ events/sched/sched_switch/trigger) do_trace_event_raw_event_##call trace_event_buffer_lock_reserve if (!tr->no_filter_buffering_ref && trace_file->flags & EVENT_FILE_FL_FILTERED) return entry; // return directly event_hist_trigger_parse hist_register_trigger tracing_set_filter_buffering(file->tr, true); tr->no_filter_buffering_ref++; __trace_buffer_lock_reserve rb_start_commit local_inc(&cpu_buffer->committing); // skipped and not executed trace_event_buffer_commit __event_trigger_test_discard event_triggers_call event_hist_trigger hist_fn_call hist_field_timestamp ring_buffer_event_time_stamp nest = local_read(&cpu_buffer->committing); WARN_ON_ONCE(!nest) // trigger warning The root cause is that when an event file has a filter attached and the hist trigger has not yet been attached, trace_event_buffer_lock_reserve() writes the event into the per-CPU trace_buffered_event temp buffer instead of reserving it in the ring buffer, so cpu_buffer->committing is not incremented. When the event is later processed at commit time by a hist trigger, hist_field_timestamp() -> ring_buffer_event_time_stamp() sees a zero committing count, triggering WARN_ON_ONCE(!nest). tracing_event_time_stamp() was added by commit d8279bfc5e959 ("tracing: Add tracing_event_time_stamp() API") for exactly this case: if the event is the per-CPU trace_buffered_event, it returns the current ring buffer timestamp. But it never gained a caller. Use it in hist_field_timestamp(), so that a hist trigger that races onto a buffered event records the current time, which is only marginally later than when the event was recorded, instead of warning and recording a bogus timestamp.
View original CVE JSON
{
"id": "CVE-2026-99140",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-28T11:17:33.960",
"lastModified": "2026-10-28T11:17:33.960",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix hist trigger timestamps for buffered events\n\nSyzkaller triggered a WARN_ON_ONCE(!nest) warning:\n\n WARNING: kernel/trace/ring_buffer.c:821 at ring_buffer_event_time_stamp\n Call trace:\n ring_buffer_event_time_stamp\n hist_field_timestamp\n hist_fn_call\n event_hist_trigger\n event_triggers_call\n __event_trigger_test_discard\n trace_event_buffer_commit\n do_trace_event_raw_event_sched_switch\n trace_event_raw_event_sched_switch\n\nThe warning is probabilistically reproducible and is related to syzkaller\nexecuting the following commands:\n\n echo 'prev_pid == 999999' > events/sched/sched_switch/filter\n echo 'hist:keys=common_timestamp' > events/sched/sched_switch/trigger\n\nThe specific triggering process is as follows:\n\nCPU 0 CPU 1\n(context switching) (echo 'hist:keys=common_timestamp' > \\\n events/sched/sched_switch/trigger)\ndo_trace_event_raw_event_##call\n trace_event_buffer_lock_reserve\n if (!tr->no_filter_buffering_ref &&\n trace_file->flags & EVENT_FILE_FL_FILTERED)\n return entry; // return directly\n event_hist_trigger_parse\n hist_register_trigger\n tracing_set_filter_buffering(file->tr, true);\n tr->no_filter_buffering_ref++;\n __trace_buffer_lock_reserve\n rb_start_commit\n local_inc(&cpu_buffer->committing); // skipped and not executed\n trace_event_buffer_commit\n __event_trigger_test_discard\n event_triggers_call\n event_hist_trigger\n hist_fn_call\n hist_field_timestamp\n ring_buffer_event_time_stamp\n nest = local_read(&cpu_buffer->committing);\n WARN_ON_ONCE(!nest) // trigger warning\n\nThe root cause is that when an event file has a filter attached and the\nhist trigger has not yet been attached, trace_event_buffer_lock_reserve()\nwrites the event into the per-CPU trace_buffered_event temp buffer instead\nof reserving it in the ring buffer, so cpu_buffer->committing is not\nincremented. When the event is later processed at commit time by a hist\ntrigger, hist_field_timestamp() -> ring_buffer_event_time_stamp() sees a\nzero committing count, triggering WARN_ON_ONCE(!nest).\n\ntracing_event_time_stamp() was added by commit d8279bfc5e959 (\"tracing:\nAdd tracing_event_time_stamp() API\") for exactly this case: if the event\nis the per-CPU trace_buffered_event, it returns the current ring buffer\ntimestamp. But it never gained a caller. Use it in hist_field_timestamp(),\nso that a hist trigger that races onto a buffered event records the\ncurrent time, which is only marginally later than when the event was\nrecorded, instead of warning and recording a bogus timestamp."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"kernel/trace/trace_events_hist.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "b94bc80df64823e676b506f8de7dcf6a688d681e",
"lessThan": "09c7cce2e59e6b3b1807520bcb1980c561f15d1e",
"versionType": "git",
"status": "affected"
},
{
"version": "b94bc80df64823e676b506f8de7dcf6a688d681e",
"lessThan": "89e90b16aadd6e66bd0323bc8dfc76a62e756b57",
"versionType": "git",
"status": "affected"
},
{
"version": "b94bc80df64823e676b506f8de7dcf6a688d681e",
"lessThan": "9414ca3b99e5a7f1f3bf51c2a01b383e1b355dd0",
"versionType": "git",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"kernel/trace/trace_events_hist.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "5.13",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.13",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.59",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2.13",
"lessThanOrEqual": "7.2.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.3",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/09c7cce2e59e6b3b1807520bcb1980c561f15d1e",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/89e90b16aadd6e66bd0323bc8dfc76a62e756b57",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/9414ca3b99e5a7f1f3bf51c2a01b383e1b355dd0",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}