[CWS] fix panic when there is no question in the DNS layer #38107

paulcacheux · 2025-06-21T08:04:27Z

What does this PR do?

This PR fixes the following panic, seen on 7.68.0rc4:

panic: runtime error: index out of range [0] with length 0
goroutine 601 [running]:
github.com/DataDog/datadog-agent/pkg/security/probe.(*EBPFProbe).handleEvent(0xc004ea8e08, 0x0, {0xc003daa580, 0xe2, 0x561})
	/omnibus/src/datadog-agent/src/github.com/DataDog/datadog-agent/pkg/security/probe/probe_ebpf.go:1353 +0x5b65
github.com/DataDog/datadog-agent/pkg/security/probe/eventstream/ringbuffer.(*RingBuffer).handleEvent(0xc000b9a270, 0xc0056be4c0, 0x0?, 0xc0013c1f38?)
	/omnibus/src/datadog-agent/src/github.com/DataDog/datadog-agent/pkg/security/probe/eventstream/ringbuffer/ringbuffer.go:60 +0x31
github.com/DataDog/ebpf-manager.(*RingBuffer).Start.func1()
	/go/pkg/mod/github.com/!data!dog/ebpf-manager@v0.7.12/ringbuffer.go:138 +0x187
created by github.com/DataDog/ebpf-manager.(*RingBuffer).Start in goroutine 1
	/go/pkg/mod/github.com/!data!dog/ebpf-manager@v0.7.12/ringbuffer.go:108 +0x125

by ensuring we check the size of dnslayer.questions before accessing the first element.

Motivation

Describe how you validated your changes

Possible Drawbacks / Trade-offs

Additional Notes

cit-pr-commenter · 2025-06-21T08:52:43Z

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 7a5f56b-23c6-4843-9989-7f17af73b6d2

Baseline: 4fb99d8
Comparison: 447e076
Diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+0.73	[-0.13, +1.60]	1	Logs
➖	ddot_logs	memory utilization	+0.71	[+0.62, +0.81]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	+0.62	[+0.57, +0.67]	1	Logs
➖	quality_gate_idle	memory utilization	+0.41	[+0.35, +0.47]	1	Logs bounds checks dashboard
➖	docker_containers_cpu	% cpu utilization	+0.37	[-2.65, +3.40]	1	Logs
➖	file_tree	memory utilization	+0.23	[+0.08, +0.38]	1	Logs
➖	ddot_metrics	memory utilization	+0.18	[+0.07, +0.30]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	+0.12	[+0.03, +0.22]	1	Logs bounds checks dashboard
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	+0.11	[+0.05, +0.16]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	+0.08	[-0.44, +0.60]	1	Logs
➖	file_to_blackhole_0ms_latency_http1	egress throughput	+0.06	[-0.54, +0.66]	1	Logs
➖	file_to_blackhole_300ms_latency	egress throughput	+0.01	[-0.60, +0.62]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	+0.01	[-0.55, +0.57]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.00	[-0.27, +0.27]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.01	[-0.02, +0.01]	1	Logs
➖	file_to_blackhole_1000ms_latency_linear_load	egress throughput	-0.01	[-0.24, +0.22]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	-0.04	[-0.68, +0.60]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	-0.04	[-0.56, +0.48]	1	Logs
➖	file_to_blackhole_0ms_latency_http2	egress throughput	-0.05	[-0.63, +0.52]	1	Logs
➖	docker_containers_memory	memory utilization	-0.11	[-0.18, -0.04]	1	Logs
➖	otlp_ingest_logs	memory utilization	-0.57	[-0.69, -0.44]	1	Logs
➖	quality_gate_logs	% cpu utilization	-0.75	[-3.48, +1.98]	1	Logs bounds checks dashboard
➖	otlp_ingest_metrics	memory utilization	-0.78	[-0.93, -0.62]	1	Logs

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	links
✅	docker_containers_cpu	simple_check_run	10/10
✅	docker_containers_memory	memory_usage	10/10
✅	docker_containers_memory	simple_check_run	10/10
✅	file_to_blackhole_0ms_latency	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency	memory_usage	10/10
✅	file_to_blackhole_0ms_latency_http1	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency_http1	memory_usage	10/10
✅	file_to_blackhole_0ms_latency_http2	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency_http2	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency_linear_load	memory_usage	10/10
✅	file_to_blackhole_100ms_latency	lost_bytes	10/10
✅	file_to_blackhole_100ms_latency	memory_usage	10/10
✅	file_to_blackhole_300ms_latency	lost_bytes	10/10
✅	file_to_blackhole_300ms_latency	memory_usage	10/10
✅	file_to_blackhole_500ms_latency	lost_bytes	10/10
✅	file_to_blackhole_500ms_latency	memory_usage	10/10
✅	quality_gate_idle	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_logs	lost_bytes	10/10	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	bounds checks dashboard

Explanation

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

Performance changes are noted in the perf column of each table:

✅ = significantly better comparison variant performance
❌ = significantly worse comparison variant performance
➖ = no significant change in performance

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.
Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.
Its configuration does not mark it "erratic".

CI Pass/Fail Decision

✅ Passed. All Quality Gates passed.

quality_gate_idle_all_features, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_idle_all_features, bounds check intake_connections: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check lost_bytes: 10/10 replicas passed. Gate passed.
quality_gate_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.

agent-platform-auto-pr · 2025-06-21T09:58:35Z

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 4fb99d8

Successful checks

Info

	Quality gate	Delta	On disk size (MiB)	Delta	On wire size (MiB)
✅	agent_deb_amd64	$${0}$$	$${697.14}$$ < $${697.37}$$	$${+26.71}$$	$${176.06}$$ < $${177.03}$$
✅	agent_deb_amd64_fips	$${+0}$$	$${695.44}$$ < $${695.59}$$	$${+25.57}$$	$${175.62}$$ < $${176.51}$$
✅	agent_heroku_amd64	$${0}$$	$${358.72}$$ < $${359.67}$$	$${+11.33}$$	$${96.53}$$ < $${97.47}$$
✅	agent_msi	$${0}$$	$${959.28}$$ < $${959.86}$$	$${-0.02}$$	$${146.27}$$ < $${147.27}$$
✅	agent_rpm_amd64	$${0}$$	$${697.13}$$ < $${697.36}$$	$${+25.87}$$	$${177.67}$$ < $${178.56}$$
✅	agent_rpm_amd64_fips	$${+0}$$	$${695.42}$$ < $${695.58}$$	$${+25.02}$$	$${177.59}$$ < $${178.43}$$
✅	agent_rpm_arm64	$${0}$$	$${687.14}$$ < $${687.37}$$	$${+22.88}$$	$${161.16}$$ < $${161.99}$$
✅	agent_rpm_arm64_fips	$${0}$$	$${685.55}$$ < $${685.72}$$	$${+21.44}$$	$${160.24}$$ < $${161.11}$$
✅	agent_suse_amd64	$${0}$$	$${697.13}$$ < $${697.36}$$	$${+25.87}$$	$${177.67}$$ < $${178.56}$$
✅	agent_suse_amd64_fips	$${+0}$$	$${695.42}$$ < $${695.58}$$	$${+25.02}$$	$${177.59}$$ < $${178.43}$$
✅	agent_suse_arm64	$${0}$$	$${687.14}$$ < $${687.37}$$	$${+22.88}$$	$${161.16}$$ < $${161.99}$$
✅	agent_suse_arm64_fips	$${0}$$	$${685.55}$$ < $${685.72}$$	$${+21.44}$$	$${160.24}$$ < $${161.11}$$
✅	docker_agent_amd64	$${-0}$$	$${780.94}$$ < $${781.16}$$	$${+0}$$	$${268.83}$$ < $${269.63}$$
✅	docker_agent_arm64	$${-0}$$	$${794.4}$$ < $${794.62}$$	$${-0.01}$$	$${256.19}$$ < $${257.0}$$
✅	docker_agent_jmx_amd64	$${-0}$$	$${972.13}$$ < $${972.35}$$	$${-0.01}$$	$${337.79}$$ < $${338.6}$$
✅	docker_agent_jmx_arm64	$${-0}$$	$${974.19}$$ < $${974.41}$$	$${+0}$$	$${321.13}$$ < $${321.97}$$
✅	docker_agent_windows1809	$${+0}$$	$${1180.85}$$ < $${1185.29}$$	$${-0.06}$$	$${416.24}$$ < $${420.95}$$
✅	docker_agent_windows1809_core	$${+0}$$	$${5910.81}$$ < $${5915.25}$$	$${0}$$	$${2048.0}$$ < $${2049.0}$$
✅	docker_agent_windows1809_core_jmx	$${+0}$$	$${6032.38}$$ < $${6059.4}$$	$${0}$$	$${2048.0}$$ < $${2049.0}$$
✅	docker_agent_windows1809_jmx	$${-0}$$	$${1302.48}$$ < $${1306.92}$$	$${+0.01}$$	$${458.53}$$ < $${463.21}$$
✅	docker_agent_windows2022	$${-0.13}$$	$${1200.15}$$ < $${1204.42}$$	$${+0.01}$$	$${428.97}$$ < $${433.71}$$
✅	docker_agent_windows2022_core	$${-0.28}$$	$${5883.37}$$ < $${5888.56}$$	$${0}$$	$${2048.0}$$ < $${2049.0}$$
✅	docker_agent_windows2022_core_jmx	$${+0.22}$$	$${6005.52}$$ < $${6009.95}$$	$${0}$$	$${2048.0}$$ < $${2049.0}$$
✅	docker_agent_windows2022_jmx	$${-0.19}$$	$${1321.54}$$ < $${1326.13}$$	$${+0}$$	$${471.25}$$ < $${475.99}$$
✅	docker_cluster_agent_amd64	$${-0}$$	$${212.89}$$ < $${213.79}$$	$${-0}$$	$${72.4}$$ < $${73.33}$$
✅	docker_cluster_agent_arm64	$${-0}$$	$${228.76}$$ < $${229.64}$$	$${-0}$$	$${68.68}$$ < $${69.6}$$
✅	docker_cws_instrumentation_amd64	$${-0}$$	$${7.08}$$ < $${7.12}$$	$${-0}$$	$${2.95}$$ < $${3.29}$$
✅	docker_cws_instrumentation_arm64	$${-0}$$	$${6.69}$$ < $${6.92}$$	$${-0}$$	$${2.7}$$ < $${3.07}$$
✅	docker_dogstatsd_amd64	$${0}$$	$${39.22}$$ < $${39.57}$$	$${-0}$$	$${15.12}$$ < $${15.76}$$
✅	docker_dogstatsd_arm64	$${+0}$$	$${37.88}$$ < $${38.2}$$	$${+0}$$	$${14.53}$$ < $${14.83}$$
✅	dogstatsd_deb_amd64	$${0}$$	$${30.45}$$ < $${31.4}$$	$${+0.08}$$	$${8.0}$$ < $${8.95}$$
✅	dogstatsd_deb_arm64	$${0}$$	$${29.02}$$ < $${29.97}$$	$${+0.09}$$	$${6.94}$$ < $${7.89}$$
✅	dogstatsd_rpm_amd64	$${0}$$	$${30.45}$$ < $${31.4}$$	$${+0.07}$$	$${8.01}$$ < $${8.96}$$
✅	dogstatsd_suse_amd64	$${0}$$	$${30.45}$$ < $${31.4}$$	$${+0.07}$$	$${8.01}$$ < $${8.96}$$
✅	iot_agent_deb_amd64	$${0}$$	$${50.47}$$ < $${51.38}$$	$${+0.25}$$	$${12.85}$$ < $${13.79}$$
✅	iot_agent_deb_arm64	$${0}$$	$${47.94}$$ < $${48.85}$$	$${+0.23}$$	$${11.15}$$ < $${12.09}$$
✅	iot_agent_deb_armhf	$${0}$$	$${47.51}$$ < $${48.42}$$	$${-0}$$	$${11.21}$$ < $${12.16}$$
✅	iot_agent_rpm_amd64	$${0}$$	$${50.47}$$ < $${51.38}$$	$${+0.24}$$	$${12.87}$$ < $${13.81}$$
✅	iot_agent_rpm_arm64	$${0}$$	$${47.94}$$ < $${48.85}$$	$${+0.23}$$	$${11.17}$$ < $${12.11}$$
✅	iot_agent_suse_amd64	$${0}$$	$${50.47}$$ < $${51.38}$$	$${+0.24}$$	$${12.87}$$ < $${13.81}$$

YoannGh · 2025-06-23T07:39:51Z

/merge

dd-devflow · 2025-06-23T07:39:54Z

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2025-06-23 08:25:58 UTC ℹ️ MergeQueue: This merge request was merged

(cherry picked from commit 17f0dd6)

[CWS] fix panic when there is no question in the DNS layer

447e076

paulcacheux added the changelog/no-changelog label Jun 21, 2025

paulcacheux requested a review from a team as a code owner June 21, 2025 08:04

paulcacheux added team/agent-security qa/done QA done before merge and regressions are covered by tests backport/7.68.x Automatically create a backport PR to 7.68.x labels Jun 21, 2025

github-actions bot added component/system-probe short review PR is simple enough to be reviewed quickly labels Jun 21, 2025

safchain approved these changes Jun 23, 2025

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YoannGh approved these changes Jun 23, 2025

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YoannGh added the category/bugfix label Jun 23, 2025

spikat approved these changes Jun 23, 2025

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dd-mergequeue bot merged commit 17f0dd6 into main Jun 23, 2025
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dd-mergequeue bot deleted the paulcacheux/fix-panic-no-question branch June 23, 2025 08:25

github-actions bot added this to the 7.69.0 milestone Jun 23, 2025

agent-platform-auto-pr bot pushed a commit that referenced this pull request Jun 23, 2025

[CWS] fix panic when there is no question in the DNS layer (#38107)

0210ee6

(cherry picked from commit 17f0dd6)

agent-platform-auto-pr bot mentioned this pull request Jun 23, 2025

[Backport 7.68.x] [CWS] fix panic when there is no question in the DNS layer #38113

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[CWS] fix panic when there is no question in the DNS layer #38107

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Fine details of change detection per experiment

Bounds Checks: ✅ Passed

Explanation

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[CWS] fix panic when there is no question in the DNS layer #38107

[CWS] fix panic when there is no question in the DNS layer #38107

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What does this PR do?

Motivation

Describe how you validated your changes

Possible Drawbacks / Trade-offs

Additional Notes

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Regression Detector

Regression Detector Results

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

Bounds Checks: ✅ Passed

Explanation

CI Pass/Fail Decision

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Static quality checks

Info

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