fix(logs): disable symlink following for process_log-discovered paths

[vitkyrka]

What does this PR do?

Hardens the log tailer against symlink-following for log paths discovered via the process_log autodiscovery provider.

• Adds a NoFollow bool field to LogsConfig (comp/logs/agent/config/integration_config.go), set by the AD scheduler whenever a source's provider is process_log (pkg/logs/schedulers/ad/scheduler.go).
• Adds OpenLogFileNoFollow / OpenNoFollow / OpenPrivilegedNoFollow variants across the file-opener stack (pkg/logs/internal/util/opener, pkg/logs/util/opener, pkg/privileged-logs/client), all backed by a new common.OpenPathWithoutSymlinks helper (pkg/privileged-logs/common/open_linux.go) that walks each path component with O_NOFOLLOW. This helper is shared by both the privileged-logs client (agent side) and the privileged-logs module (system-probe side), so the no-follow behavior is enforced whether or not privileged log collection is used.
• The file tailer (pkg/logs/tailers/file/tailer.go) and fingerprinter (pkg/logs/tailers/file/fingerprint.go) now route through a noFollow-aware open on every open site (initial open, rotation re-open, fingerprinting), driven by Source.Config().NoFollow. Tailer.ReplaceSource refreshes this flag when a source is replaced.
• NoFollow is propagated to container/k8s-derived sources in pkg/logs/launchers/container/tailerfactory/file.go. Container/pod log paths (e.g. /var/log/pods/…) are intentionally symlinked by the runtime, so those sources continue to follow symlinks as before — only process_log-originated sources get NoFollow.
• checkFileReadable in the process_log provider (comp/core/autodiscovery/providers/process_log.go) uses the no-follow open when validating a discovered path is readable.

Other log sources (file, kubernetes, etc.) are unaffected: their paths are explicitly specified by the user, and it's up to the user to ensure such a path isn't swapped for a symlink by an untrusted party.

Motivation

Paths discovered via process_log come from readlink(/proc/<pid>/fd/<n>). The kernel resolves all symlinks at the time the target process opened that fd, so the string returned is already canonical — if a symlink appears at that path later, it was planted after discovery by something other than the process that owns the fd. Since the agent otherwise follows symlinks when tailing, an unprivileged attacker able to write to the resolved path could swap it for a symlink and get the agent to tail an arbitrary dd-agent-readable file (or a root-readable one, if privileged log collection is enabled).

Rejecting symlinks for this specific, narrow case (process_log-discovered paths only) closes that gap without changing behavior for any other log collection method that legitimately relies on symlinks.

Tracked internally in DSCVR-475.

Describe how you validated your changes

Added unit tests covering both the policy and the low-level enforcement:

• TestNoFollowFlagSetOnConfig (pkg/logs/schedulers/ad/scheduler_test.go): sources from process_log get NoFollow=true; sources from file/kubernetes do not.
• TestReplaceSourceRefreshesNoFollow (pkg/logs/tailers/file/tailer_test.go): ReplaceSource updates the tailer's no-follow state.
• TestOpenPathWithoutSymlinks* (pkg/privileged-logs/common/open_linux_test.go): no symlink present, symlink as the final component, symlink in a parent directory, and the swap scenario (open succeeds, file removed and replaced with a symlink, second open is rejected with ELOOP).
• TestLauncherNoFollowSymlink / TestPrivilegedLogsLauncherNoFollowSymlink (pkg/logs/launchers/file/launcher_test.go, launcher_privileged_logs_test.go): end-to-end launcher coverage for both the unprivileged and system-probe-backed (privileged logs) open paths.

Additional Notes

names.ProcessLog (the autodiscovery provider name constant) is unchanged — it identifies the provider, not the config flag.

[github-actions]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🚀

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[datadog-official]

🎯 Code Coverage (details)
• Patch Coverage: 44.44%
• Overall Coverage: 52.20% (+0.13%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: ce83f4a | Docs | Datadog PR Page | Give us feedback!}

[dd-octo-sts]

Files inventory check summary

File checks results against ancestor 83b0223d:

Results for datadog-agent_7.83.0~devel.git.492.ce83f4a.pipeline.128204586-1_amd64.deb:

No change detected

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 4761bad0-abde-4d8b-b1d4-1b015ab163f8

Baseline: 83b0223
Comparison: ce83f4a
Diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_idle	memory utilization	+0.45	[+0.40, +0.50]	1	Logs bounds checks dashboard
➖	quality_gate_private_action_runner	memory utilization	+0.38	[+0.26, +0.50]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	+0.19	[-0.06, +0.44]	1	Logs bounds checks dashboard
➖	quality_gate_security_mean_fs_load	memory utilization	+0.13	[+0.10, +0.17]	1	Logs bounds checks dashboard
➖	quality_gate_security_no_fs_load	memory utilization	+0.01	[-0.07, +0.10]	1	Logs bounds checks dashboard
➖	quality_gate_logs	% cpu utilization	+0.00	[-1.00, +1.00]	1	Logs bounds checks dashboard
➖	quality_gate_idle_all_features	memory utilization	-0.01	[-0.04, +0.03]	1	Logs bounds checks dashboard
➖	quality_gate_security_idle	memory utilization	-0.25	[-0.30, -0.19]	1	Logs bounds checks dashboard

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	observed_value	links
✅	quality_gate_idle	intake_connections	10/10	3 ≤ 4	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	150.64MiB ≤ 154MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	733.92KiB ≤ 819.20KiB	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	3 ≤ 4	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	491.22MiB ≤ 512MiB	bounds checks dashboard
✅	quality_gate_idle_all_features	total_bytes_received	10/10	1.12MiB ≤ 1.25MiB	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	4 ≤ 6	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	186.47MiB ≤ 195MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	264.17MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	386.83 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	3 ≤ 6	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	413.86MiB ≤ 430MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_metrics_logs	total_bytes_received	10/10	0.94GiB ≤ 1.04GiB	bounds checks dashboard
✅	quality_gate_private_action_runner	memory_usage	10/10	72.37MiB ≤ 75MiB	bounds checks dashboard
✅	quality_gate_security_idle	cpu_usage	10/10	29.56 ≤ 100	bounds checks dashboard
✅	quality_gate_security_idle	memory_usage	10/10	300.73MiB ≤ 330MiB	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	cpu_usage	10/10	62.78 ≤ 200	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	memory_usage	10/10	280.12MiB ≤ 310MiB	bounds checks dashboard
✅	quality_gate_security_no_fs_load	cpu_usage	10/10	20.59 ≤ 100	bounds checks dashboard
✅	quality_gate_security_no_fs_load	memory_usage	10/10	282.99MiB ≤ 320MiB	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".

Replicate Execution Details

We run multiple replicates for each experiment/variant. However, we allow replicates to be automatically retried if there are any failures, up to 8 times, at which point the replicate is marked dead and we are unable to run analysis for the entire experiment. We call each of these attempts at running replicates a replicate execution. This section lists all replicate executions that failed due to the target crashing or being oom killed.

Note: In the below tables we bucket failures by experiment, variant, and failure type. For each of these buckets we list out the replicate indexes that failed with an annotation signifying how many times said replicate failed with the given failure mode. In the below example the baseline variant of the experiment named experiment_with_failures had two replicates that failed by oom kills. Replicate 0, which failed 8 executions, and replicate 1 which failed 6 executions, all with the same failure mode.

Experiment	Variant	Replicates	Failure	Logs	Debug Dashboard
experiment_with_failures	baseline	0 (x8) 1 (x6)	Oom killed		Debug Dashboard

The debug dashboard links will take you to a debugging dashboard specifically designed to investigate replicate execution failures.

❌ Retried Profiling Replicate Execution Failures (ddprof)

Note: Profiling replicas may still be executing. See the debug dashboard for up to date status.

Experiment	Variant	Replicates	Failure	Debug Dashboard
quality_gate_idle	baseline	10	Oom killed	Debug Dashboard
quality_gate_idle_all_features	baseline	10	Oom killed	Debug Dashboard
quality_gate_idle_all_features	comparison	10	Oom killed	Debug Dashboard
quality_gate_logs	baseline	10	Oom killed	Debug Dashboard
quality_gate_logs	comparison	10	Oom killed	Debug Dashboard
quality_gate_metrics_logs	baseline	10	Oom killed	Debug Dashboard
quality_gate_metrics_logs	comparison	10	Oom killed	Debug Dashboard
quality_gate_security_idle	baseline	10	Oom killed	Debug Dashboard
quality_gate_security_idle	comparison	10	Crashed (exit code: 134)	Debug Dashboard
quality_gate_security_no_fs_load	comparison	10	Crashed (exit code: 134)	Debug Dashboard

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_all_features, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_private_action_runner, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check missed_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check total_bytes_received: 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.
• quality_gate_security_no_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_no_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check missed_bytes: 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_security_mean_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_mean_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.

[github-actions]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

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[dd-octo-sts]

This pull request has been automatically marked as stale because it has not had activity in the past 15 days.

It will be closed in 30 days if no further activity occurs. If this pull request is still relevant, adding a comment or pushing new commits will keep it open. Also, you can always reopen the pull request if you missed the window.

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[dd-octo-sts]

This pull request has been automatically marked as stale because it has not had activity in the past 15 days.

It will be closed in 30 days if no further activity occurs. If this pull request is still relevant, adding a comment or pushing new commits will keep it open. Also, you can always reopen the pull request if you missed the window.

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[dd-octo-sts]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 83b0223
📊 Static Quality Gates Dashboard
🔗 SQG Job

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64	+8.0 KiB (0.00% increase, -0.14% of buffer)	752.727 → 752.735 → 758.200
✅	agent_deb_amd64_fips	+12.0 KiB (0.00% increase, -0.38% of buffer)	707.430 → 707.441 → 710.520
✅	agent_heroku_amd64	+8.0 KiB (0.00% increase, -0.11% of buffer)	308.129 → 308.137 → 315.230
✅	agent_rpm_amd64	+8.0 KiB (0.00% increase, -0.14% of buffer)	752.711 → 752.719 → 758.170
✅	agent_rpm_amd64_fips	+12.0 KiB (0.00% increase, -0.38% of buffer)	707.413 → 707.425 → 710.520
✅	agent_rpm_arm64	+8.0 KiB (0.00% increase, -1.91% of buffer)	729.252 → 729.260 → 729.660
✅	agent_rpm_arm64_fips	+4.0 KiB (0.00% increase, -0.22% of buffer)	687.120 → 687.124 → 688.910
✅	agent_suse_amd64	+8.0 KiB (0.00% increase, -0.14% of buffer)	752.711 → 752.719 → 758.170
✅	agent_suse_amd64_fips	+12.0 KiB (0.00% increase, -0.38% of buffer)	707.413 → 707.425 → 710.520
✅	agent_suse_arm64	+8.0 KiB (0.00% increase, -1.91% of buffer)	729.252 → 729.260 → 729.660
✅	agent_suse_arm64_fips	+4.0 KiB (0.00% increase, -0.22% of buffer)	687.120 → 687.124 → 688.910
✅	docker_agent_amd64	+8.0 KiB (0.00% increase, -0.32% of buffer)	811.383 → 811.391 → 813.790
✅	docker_agent_arm64	+7.99 KiB (0.00% increase, -0.38% of buffer)	812.987 → 812.995 → 815.030
✅	docker_agent_jmx_amd64	+8.0 KiB (0.00% increase, -0.34% of buffer)	1002.281 → 1002.288 → 1004.550
✅	docker_agent_jmx_arm64	+8.0 KiB (0.00% increase, -0.36% of buffer)	992.537 → 992.545 → 994.710
✅	iot_agent_deb_amd64	+8.0 KiB (0.02% increase, -4.66% of buffer)	46.212 → 46.220 → 46.380
✅	iot_agent_deb_arm64	+4.0 KiB (0.01% increase, -0.48% of buffer)	42.900 → 42.903 → 43.720
✅	iot_agent_deb_armhf	+8.0 KiB (0.02% increase, -2.61% of buffer)	43.660 → 43.668 → 43.960
✅	iot_agent_rpm_amd64	+8.0 KiB (0.02% increase, -4.67% of buffer)	46.213 → 46.220 → 46.380
✅	iot_agent_suse_amd64	+8.0 KiB (0.02% increase, -4.64% of buffer)	46.212 → 46.219 → 46.380

13 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_msi	638.324 MiB
✅	docker_cluster_agent_amd64	209.932 MiB
✅	docker_cluster_agent_arm64	223.011 MiB
✅	docker_cws_instrumentation_amd64	7.439 MiB
✅	docker_cws_instrumentation_arm64	6.877 MiB
✅	docker_dogstatsd_amd64	39.262 MiB
✅	docker_dogstatsd_arm64	37.367 MiB
✅	docker_host_profiler_amd64	305.308 MiB
✅	docker_host_profiler_arm64	316.621 MiB
✅	dogstatsd_deb_amd64	30.007 MiB
✅	dogstatsd_deb_arm64	28.043 MiB
✅	dogstatsd_rpm_amd64	30.007 MiB
✅	dogstatsd_suse_amd64	30.007 MiB

[dd-octo-sts]

This pull request has been automatically marked as stale because it has not had activity in the past 15 days.

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