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CVE Record

CVE-2025-21889: perf/core: Add RCU read lock protection to perf_iterate_ctx()

In the Linux kernel, the following vulnerability has been resolved: perf/core: Add RCU read lock protection to perf_iterate_ctx() The perf_iterate_ctx() function performs RCU list traversal but currently lacks RCU read lock protection. This causes lockdep warnings when running perf probe with unshare(1) under CONFIG_PROVE_RCU_LIST=y: WARNING: suspicious RCU usage kernel/events/core.c:8168 RCU-list traversed in non-reader section!! Call Trace: lockdep_rcu_suspicious ? perf_event_addr_filters_apply perf_iterate_ctx perf_event_exec begin_new_exec ? load_elf_phdrs load_elf_binary ? lock_acquire ? find_held_lock ? bprm_execve bprm_execve do_execveat_common.isra.0 __x64_sys_execve do_syscall_64 entry_SYSCALL_64_after_hwframe This protection was previously present but was removed in commit bd2756811766 ("perf: Rewrite core context handling"). Add back the necessary rcu_read_lock()/rcu_read_unlock() pair around perf_iterate_ctx() call in perf_event_exec(). [ mingo: Use scoped_guard() as suggested by Peter ]

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2025-21889 is a Linux kernel perf subsystem issue where a needed RCU read lock was missing. The public record shows a kernel warning during a specific perf/unshare scenario, but does not describe data theft, privilege escalation, denial of service, or active exploitation.

Executive priority

Treat as a routine kernel hygiene item unless vendor guidance assigns higher severity. There is no sourced evidence of active exploitation or clear business-impacting consequence, but kernel updates should stay on normal patch cycles.

Technical view

perf_iterate_ctx() performs RCU list traversal without RCU read-side protection when called from perf_event_exec(). The fix restores rcu_read_lock()/rcu_read_unlock() coverage, implemented with scoped_guard(), after earlier context-handling changes removed it.

Likely exposure

Exposure is limited to Linux systems running affected kernel versions or branches containing the referenced regression and lacking the stable fixes. Distro package backports may change exposure, so validate against vendor kernel advisories and changelogs.

Exploitation context

The sources only document lockdep warnings under CONFIG_PROVE_RCU_LIST=y when running perf probe with unshare(1). CISA KEV status is false, and no cited source confirms exploitation in the wild.

Researcher notes

Impact evidence is incomplete. The record describes an RCU correctness bug detected by lockdep, not a demonstrated exploit primitive. Focus validation on whether downstream kernels include one of the stable fixes or equivalent backport.

Mitigation direction

  • Apply vendor kernel updates that include the cited stable fixes.
  • Check Linux distribution advisories for affected and fixed package versions.
  • Track upstream stable commits only as supporting evidence, not package status.
  • Prioritize systems allowing local perf use if vendor guidance raises impact.

Validation and detection

  • Inventory Linux kernel versions across servers, workstations, and images.
  • Map installed kernel packages to distro advisories for CVE-2025-21889.
  • Review kernel changelogs for the perf_event_exec RCU protection fix.
  • Confirm vulnerability scanners recognize vendor-fixed kernel packages.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
5Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxbd27568117664b8b3e259721393df420ed51f57b, bd27568117664b8b3e259721393df420ed51f57b, bd27568117664b8b3e259721393df420ed51f57b, bd27568117664b8b3e259721393df420ed51f57bunaffected
LinuxLinux6.2, 0, 6.6.81, 6.12.18, 6.13.6, 6.14affected
Weakness

CWE details

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