{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-21889",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-21889"
  ],
  "published": "2025-03-27T15:01:31Z",
  "summary": "perf/core: Add RCU read lock protection to perf_iterate_ctx()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Add RCU read lock protection to perf_iterate_ctx()\n\nThe perf_iterate_ctx() function performs RCU list traversal but\ncurrently lacks RCU read lock protection. This causes lockdep warnings\nwhen running perf probe with unshare(1) under CONFIG_PROVE_RCU_LIST=y:\n\n\tWARNING: suspicious RCU usage\n\tkernel/events/core.c:8168 RCU-list traversed in non-reader section!!\n\n\t Call Trace:\n\t  lockdep_rcu_suspicious\n\t  ? perf_event_addr_filters_apply\n\t  perf_iterate_ctx\n\t  perf_event_exec\n\t  begin_new_exec\n\t  ? load_elf_phdrs\n\t  load_elf_binary\n\t  ? lock_acquire\n\t  ? find_held_lock\n\t  ? bprm_execve\n\t  bprm_execve\n\t  do_execveat_common.isra.0\n\t  __x64_sys_execve\n\t  do_syscall_64\n\t  entry_SYSCALL_64_after_hwframe\n\nThis protection was previously present but was removed in commit\nbd2756811766 (\"perf: Rewrite core context handling\"). Add back the\nnecessary rcu_read_lock()/rcu_read_unlock() pair around\nperf_iterate_ctx() call in perf_event_exec().\n\n[ mingo: Use scoped_guard() as suggested by Peter ]",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-21889"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f390c2eea571945f357a2d3b9fcb1c015767132e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a2475ccad6120546ea45dbcd6cd1f74dc565ef6b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/dd536566dda9a551fc2a2acfab5313a5bb13ed02"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/0fe8813baf4b2e865d3b2c735ce1a15b86002c74"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerable path is entered through local syscalls only \u2014 `execve()` reaching `perf_event_exec()` via `begin_new_exec()`, with the racing side driven by `perf_event_open()`/`close()`. No network or remote input reaches this code.\nAC:L - The attacker controls both sides of the race, looping `execve()` in one process while closing perf event fds attached to it from another, and can widen the window arbitrarily via CPU pinning and the cross-CPU IPI that `perf_event_stop()` issues inside the unprotected walk. Nothing about the trigger depends on conditions outside the attacker's influence.\nPR:L - An ordinary unprivileged user suffices: `sysctl_perf_event_paranoid` defaults to 2, which permits task-bound user-space perf events on same-uid processes, and no capability is checked anywhere on the `execve()` side of the race.\nUI:N - Both the exec'ing process and the event-closing process are attacker-controlled; no victim action or cooperation is needed.\nS:U - The corruption stays within the kernel's own security authority \u2014 a standard local kernel memory-safety flaw with no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - The unprotected RCU walk dereferences a freed `struct perf_event`, and the reclaimed slot can be groomed with attacker-sprayed perf events, giving a use-after-free read primitive that leaks kernel memory and pointers.\nI:H - `perf_event_addr_filters_exec()` writes into the freed object \u2014 zeroing `addr_filter_ranges[count].start/.size` through a pointer read out of reclaimed memory and incrementing `addr_filters_gen` \u2014 yielding an attacker-influenced kernel write suitable for privilege escalation.\nA:H - Traversing a freed list entry corrupts the walk and readily produces list corruption, an oops, or a full kernel panic, and the race can be retriggered in a loop."
    }
  }
}