[CWS] Fix cgroup resolver LRU corruption

[YoannGh]

What does this PR do?

simplelru.LRU.Get() is a mutating operation, it calls MoveToFront() to update the LRU ordering. However, four methods (GetCacheEntryContainerID, GetCacheEntryByCgroupID, GetCacheEntryByInode, and IterateCacheEntries) used RLock(), allowing multiple goroutines to concurrently call Get() and corrupt the internal doubly-linked list of the LRU. When DelPID later called Values(), it traversed the corrupted list, producing a shorter iteration than len(c.items), leaving trailing nil entries in the returned slice, causing the nil pointer dereference in ContainsPID

To fix this, this PR changes all four methods from using RLock/RUnlock to Lock/Unlock, and downgrades sync.RWMutex to sync.Mutex since the read/write distinction is no longer applicable (all LRU access requires exclusive locking due to Get() mutating the LRU)

Motivation

Fix cgroup resolver LRU corruption causing segfault like the following, as well as the one in #46508

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x17882cc]
goroutine 1006 [running]:
github.com/DataDog/datadog-agent/pkg/security/resolvers/cgroup/model.(*CacheEntry).ContainsPID(0x0, 0x391935)
github.com/DataDog/datadog-agent/pkg/security/resolvers/cgroup/model/model.go:175 +0x2c
github.com/DataDog/datadog-agent/pkg/security/resolvers/cgroup.(*Resolver).deleteCacheEntryPID(0x40012cbd40, 0x391935, 0x0)
github.com/DataDog/datadog-agent/pkg/security/resolvers/cgroup/resolver.go:437 +0x2c
github.com/DataDog/datadog-agent/pkg/security/resolvers/cgroup.(*Resolver).DelPID(0x40012cbd40, 0x391935)
github.com/DataDog/datadog-agent/pkg/security/resolvers/cgroup/resolver.go:427 +0x140
github.com/DataDog/datadog-agent/pkg/security/resolvers/process.(*EBPFResolver).deleteEntry(0x4001e20900, 0x21f2008?, {0x24efc40?, 0x40021f2008?, 0x3cfbaa0?})
github.com/DataDog/datadog-agent/pkg/security/resolvers/process/resolver_ebpf.go:657 +0x64
github.com/DataDog/datadog-agent/pkg/security/resolvers/process.(*EBPFResolver).DeleteEntry(0x4001e20900, 0x391935, {0x1?, 0x60?, 0x3cfbaa0?})
github.com/DataDog/datadog-agent/pkg/security/resolvers/process/resolver_ebpf.go:669 +0x74
github.com/DataDog/datadog-agent/pkg/security/probe.(*EBPFProbe).handleEvent(0x4000465008, 0x0, {0x4003170900, 0x60, 0x20c})
github.com/DataDog/datadog-agent/pkg/security/probe/probe_ebpf.go:1191 +0x508
github.com/DataDog/datadog-agent/pkg/security/probe/eventstream/ringbuffer.(*RingBuffer).handleEvent(0x4001da3350, 0x4006ce7860, 0x4000a95f58?, 0x4008db9f30?)
github.com/DataDog/datadog-agent/pkg/security/probe/eventstream/ringbuffer/ringbuffer.go:60 +0x3c
github.com/DataDog/ebpf-manager.(*RingBuffer).Start.func1()
github.com/DataDog/ebpf-manager@v0.7.15/ringbuffer.go:138 +0x15c
created by github.com/DataDog/ebpf-manager.(*RingBuffer).Start in goroutine 1
github.com/DataDog/ebpf-manager@v0.7.15/ringbuffer.go:108 +0x140

Describe how you validated your changes

Additional Notes

[agent-platform-auto-pr]

Files inventory check summary

File checks results against ancestor cded3a15:

Results for datadog-agent_7.77.0~devel.git.771.83c1d21.pipeline.97924831-1_amd64.deb:

Detected file changes:

1 Removed files:

• opt/datadog-agent/embedded/lib/libdatadog-agent-rtloader.so.2 (34.0 B)

1 Changed files:

• opt/datadog-agent/embedded/lib/libdatadog-agent-rtloader.so:
  • Size changed: +13.33% (30.0 B -> 34.0 B)

[agent-platform-auto-pr]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor cded3a1
📊 Static Quality Gates Dashboard
🔗 SQG Job

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	+4.26 KiB (0.00% increase)	755.988 → 755.992 → 759.670
✅	agent_rpm_amd64	+4.26 KiB (0.00% increase)	755.971 → 755.976 → 759.640
✅	agent_rpm_arm64_fips	+4.31 KiB (0.00% increase)	696.201 → 696.205 → 703.390
✅	agent_suse_amd64	+4.26 KiB (0.00% increase)	755.971 → 755.976 → 759.640
✅	agent_suse_arm64_fips	+4.31 KiB (0.00% increase)	696.201 → 696.205 → 703.390
✅	docker_agent_amd64	+4.3 KiB (0.00% increase)	817.021 → 817.026 → 821.990
✅	docker_agent_jmx_amd64	+4.27 KiB (0.00% increase)	1007.933 → 1007.937 → 1012.870
✅	docker_cluster_agent_amd64	+24.0 KiB (0.01% increase)	192.318 → 192.342 → 193.610
✅	docker_cluster_agent_arm64	+63.99 KiB (0.03% increase)	207.582 → 207.644 → 208.190

22 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_deb_amd64_fips	715.077 MiB
✅	agent_heroku_amd64	323.754 MiB
✅	agent_msi	622.073 MiB
✅	agent_rpm_amd64_fips	715.061 MiB
✅	agent_rpm_arm64	734.126 MiB
✅	agent_suse_amd64_fips	715.061 MiB
✅	agent_suse_arm64	734.126 MiB
✅	docker_agent_arm64	819.911 MiB
✅	docker_agent_jmx_arm64	999.605 MiB
✅	docker_cws_instrumentation_amd64	7.135 MiB
✅	docker_cws_instrumentation_arm64	6.689 MiB
✅	docker_dogstatsd_amd64	38.500 MiB
✅	docker_dogstatsd_arm64	36.812 MiB
✅	dogstatsd_deb_amd64	29.720 MiB
✅	dogstatsd_deb_arm64	27.881 MiB
✅	dogstatsd_rpm_amd64	29.720 MiB
✅	dogstatsd_suse_amd64	29.720 MiB
✅	iot_agent_deb_amd64	42.617 MiB
✅	iot_agent_deb_arm64	39.723 MiB
✅	iot_agent_deb_armhf	40.447 MiB
✅	iot_agent_rpm_amd64	42.618 MiB
✅	iot_agent_suse_amd64	42.618 MiB

On-wire sizes (compressed)

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	-15.41 KiB (0.01% reduction)	185.426 → 185.411 → 186.090
✅	agent_deb_amd64_fips	-62.48 KiB (0.03% reduction)	176.326 → 176.265 → 180.330
✅	agent_heroku_amd64	neutral	87.104 MiB → 88.440
✅	agent_msi	-12.0 KiB (0.01% reduction)	149.215 → 149.203 → 154.470
✅	agent_rpm_amd64	-11.11 KiB (0.01% reduction)	187.310 → 187.299 → 189.170
✅	agent_rpm_amd64_fips	+36.05 KiB (0.02% increase)	178.398 → 178.433 → 181.060
✅	agent_rpm_arm64	+26.78 KiB (0.02% increase)	169.718 → 169.744 → 170.020
✅	agent_rpm_arm64_fips	+79.31 KiB (0.05% increase)	162.456 → 162.533 → 164.130
✅	agent_suse_amd64	-11.11 KiB (0.01% reduction)	187.310 → 187.299 → 189.170
✅	agent_suse_amd64_fips	+36.05 KiB (0.02% increase)	178.398 → 178.433 → 181.060
✅	agent_suse_arm64	+26.78 KiB (0.02% increase)	169.718 → 169.744 → 170.020
✅	agent_suse_arm64_fips	+79.31 KiB (0.05% increase)	162.456 → 162.533 → 164.130
✅	docker_agent_amd64	+2.76 KiB (0.00% increase)	277.759 → 277.761 → 279.410
✅	docker_agent_arm64	-4.8 KiB (0.00% reduction)	265.053 → 265.048 → 267.960
✅	docker_agent_jmx_amd64	neutral	346.403 MiB → 348.040
✅	docker_agent_jmx_arm64	neutral	329.698 MiB → 332.560
✅	docker_cluster_agent_amd64	+4.05 KiB (0.01% increase)	67.199 → 67.203 → 68.000
✅	docker_cluster_agent_arm64	+9.98 KiB (0.02% increase)	63.179 → 63.189 → 63.640
✅	docker_cws_instrumentation_amd64	neutral	2.995 MiB → 3.330
✅	docker_cws_instrumentation_arm64	neutral	2.726 MiB → 3.090
✅	docker_dogstatsd_amd64	neutral	14.900 MiB → 15.820
✅	docker_dogstatsd_arm64	neutral	14.239 MiB → 14.830
✅	dogstatsd_deb_amd64	neutral	7.853 MiB → 8.790
✅	dogstatsd_deb_arm64	neutral	6.741 MiB → 7.710
✅	dogstatsd_rpm_amd64	neutral	7.866 MiB → 8.800
✅	dogstatsd_suse_amd64	neutral	7.866 MiB → 8.800
✅	iot_agent_deb_amd64	-2.6 KiB (0.02% reduction)	11.239 → 11.236 → 12.040
✅	iot_agent_deb_arm64	+2.74 KiB (0.03% increase)	9.601 → 9.603 → 10.450
✅	iot_agent_deb_armhf	neutral	9.804 MiB → 10.620
✅	iot_agent_rpm_amd64	neutral	11.254 MiB → 12.060
✅	iot_agent_suse_amd64	neutral	11.254 MiB → 12.060

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 592f97f9-0228-4301-a75e-62560e1a3685

Baseline: 9fac229
Comparison: 83c1d21
Diff

Optimization Goals: ✅ No significant changes detected

Experiments ignored for regressions

Regressions in experiments with settings containing erratic: true are ignored.

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
❌	docker_containers_cpu	% cpu utilization	+5.71	[+2.55, +8.87]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
❌	docker_containers_cpu	% cpu utilization	+5.71	[+2.55, +8.87]	1	Logs
➖	quality_gate_logs	% cpu utilization	+1.02	[-0.48, +2.51]	1	Logs bounds checks dashboard
➖	otlp_ingest_logs	memory utilization	+0.22	[+0.12, +0.32]	1	Logs
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	+0.05	[-0.00, +0.10]	1	Logs
➖	quality_gate_idle	memory utilization	+0.03	[-0.01, +0.08]	1	Logs bounds checks dashboard
➖	file_to_blackhole_500ms_latency	egress throughput	+0.03	[-0.35, +0.41]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.01	[-0.12, +0.14]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.00	[-0.09, +0.08]	1	Logs
➖	uds_dogstatsd_to_api_v3	ingress throughput	-0.01	[-0.13, +0.12]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	-0.01	[-0.47, +0.44]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	-0.04	[-0.46, +0.39]	1	Logs
➖	file_tree	memory utilization	-0.04	[-0.09, +0.01]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	-0.05	[-0.10, -0.01]	1	Logs
➖	docker_containers_memory	memory utilization	-0.11	[-0.19, -0.04]	1	Logs
➖	ddot_metrics_sum_delta	memory utilization	-0.15	[-0.34, +0.04]	1	Logs
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	-0.21	[-0.44, +0.02]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.24	[-0.27, -0.20]	1	Logs bounds checks dashboard
➖	tcp_syslog_to_blackhole	ingress throughput	-0.36	[-0.44, -0.28]	1	Logs
➖	ddot_logs	memory utilization	-0.46	[-0.53, -0.40]	1	Logs
➖	otlp_ingest_metrics	memory utilization	-0.57	[-0.73, -0.41]	1	Logs
➖	ddot_metrics	memory utilization	-0.75	[-0.94, -0.55]	1	Logs
➖	ddot_metrics_sum_cumulative	memory utilization	-0.75	[-0.90, -0.59]	1	Logs
➖	quality_gate_metrics_logs	memory utilization	-0.92	[-1.12, -0.72]	1	Logs bounds checks dashboard

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_1000ms_latency	lost_bytes	10/10
✅	file_to_blackhole_1000ms_latency	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_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
✅	quality_gate_metrics_logs	cpu_usage	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	lost_bytes	10/10	bounds checks dashboard
✅	quality_gate_metrics_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:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. 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.

3. 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_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_logs, 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 lost_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check lost_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check cpu_usage: 10/10 replicas passed. Gate passed.

[rdesgroppes]

Something to backport to 7.76.x?

[YoannGh]

Something to backport to 7.76.x?

Yes 👍 I opened backport PRs to both 7.76.x and 7.77.x branches