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CVE-2025-21895 (GCVE-0-2025-21895)

Vulnerability from cvelistv5 – Published: 2025-04-01 15:26 – Updated: 2026-05-11 21:08
VLAI
Title
perf/core: Order the PMU list to fix warning about unordered pmu_ctx_list
Summary
In the Linux kernel, the following vulnerability has been resolved: perf/core: Order the PMU list to fix warning about unordered pmu_ctx_list Syskaller triggers a warning due to prev_epc->pmu != next_epc->pmu in perf_event_swap_task_ctx_data(). vmcore shows that two lists have the same perf_event_pmu_context, but not in the same order. The problem is that the order of pmu_ctx_list for the parent is impacted by the time when an event/PMU is added. While the order for a child is impacted by the event order in the pinned_groups and flexible_groups. So the order of pmu_ctx_list in the parent and child may be different. To fix this problem, insert the perf_event_pmu_context to its proper place after iteration of the pmu_ctx_list. The follow testcase can trigger above warning: # perf record -e cycles --call-graph lbr -- taskset -c 3 ./a.out & # perf stat -e cpu-clock,cs -p xxx // xxx is the pid of a.out test.c void main() { int count = 0; pid_t pid; printf("%d running\n", getpid()); sleep(30); printf("running\n"); pid = fork(); if (pid == -1) { printf("fork error\n"); return; } if (pid == 0) { while (1) { count++; } } else { while (1) { count++; } } } The testcase first opens an LBR event, so it will allocate task_ctx_data, and then open tracepoint and software events, so the parent context will have 3 different perf_event_pmu_contexts. On inheritance, child ctx will insert the perf_event_pmu_context in another order and the warning will trigger. [ mingo: Tidied up the changelog. ]
Severity
4.7 (Medium)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: bd27568117664b8b3e259721393df420ed51f57b , < f0c3971405cef6892844016aa710121a02da3a23 (git)
Affected: bd27568117664b8b3e259721393df420ed51f57b , < 7d582eb6e4e100959ba07083d7563453c8c2a343 (git)
Affected: bd27568117664b8b3e259721393df420ed51f57b , < 3e812a70732d84b7873cea61a7f6349b9a9dcbf5 (git)
Affected: bd27568117664b8b3e259721393df420ed51f57b , < 2016066c66192a99d9e0ebf433789c490a6785a2 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.2
Unaffected: 0 , < 6.2 (semver)
Unaffected: 6.6.81 , ≤ 6.6.* (semver)
Unaffected: 6.12.18 , ≤ 6.12.* (semver)
Unaffected: 6.13.6 , ≤ 6.13.* (semver)
Unaffected: 6.14 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Order the PMU list to fix warning about unordered pmu_ctx_list\n\nSyskaller triggers a warning due to prev_epc-\u003epmu != next_epc-\u003epmu in\nperf_event_swap_task_ctx_data(). vmcore shows that two lists have the same\nperf_event_pmu_context, but not in the same order.\n\nThe problem is that the order of pmu_ctx_list for the parent is impacted by\nthe time when an event/PMU is added. While the order for a child is\nimpacted by the event order in the pinned_groups and flexible_groups. So\nthe order of pmu_ctx_list in the parent and child may be different.\n\nTo fix this problem, insert the perf_event_pmu_context to its proper place\nafter iteration of the pmu_ctx_list.\n\nThe follow testcase can trigger above warning:\n\n # perf record -e cycles --call-graph lbr -- taskset -c 3 ./a.out \u0026\n # perf stat -e cpu-clock,cs -p xxx // xxx is the pid of a.out\n\n test.c\n\n void main() {\n        int count = 0;\n        pid_t pid;\n\n        printf(\"%d running\\n\", getpid());\n        sleep(30);\n        printf(\"running\\n\");\n\n        pid = fork();\n        if (pid == -1) {\n                printf(\"fork error\\n\");\n                return;\n        }\n        if (pid == 0) {\n                while (1) {\n                        count++;\n                }\n        } else {\n                while (1) {\n                        count++;\n                }\n        }\n }\n\nThe testcase first opens an LBR event, so it will allocate task_ctx_data,\nand then open tracepoint and software events, so the parent context will\nhave 3 different perf_event_pmu_contexts. On inheritance, child ctx will\ninsert the perf_event_pmu_context in another order and the warning will\ntrigger.\n\n[ mingo: Tidied up the changelog. ]"
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          "url": "https://git.kernel.org/stable/c/2016066c66192a99d9e0ebf433789c490a6785a2"
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    "datePublished": "2025-04-01T15:26:48.607Z",
    "dateReserved": "2024-12-29T08:45:45.783Z",
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So\\nthe order of pmu_ctx_list in the parent and child may be different.\\n\\nTo fix this problem, insert the perf_event_pmu_context to its proper place\\nafter iteration of the pmu_ctx_list.\\n\\nThe follow testcase can trigger above warning:\\n\\n # perf record -e cycles --call-graph lbr -- taskset -c 3 ./a.out \u0026\\n # perf stat -e cpu-clock,cs -p xxx // xxx is the pid of a.out\\n\\n test.c\\n\\n void main() {\\n        int count = 0;\\n        pid_t pid;\\n\\n        printf(\\\"%d running\\\\n\\\", getpid());\\n        sleep(30);\\n        printf(\\\"running\\\\n\\\");\\n\\n        pid = fork();\\n        if (pid == -1) {\\n                printf(\\\"fork error\\\\n\\\");\\n                return;\\n        }\\n        if (pid == 0) {\\n                while (1) {\\n                        count++;\\n                }\\n        } else {\\n                while (1) {\\n                        count++;\\n                }\\n        }\\n }\\n\\nThe testcase first opens an LBR event, so it will allocate task_ctx_data,\\nand then open tracepoint and software events, so the parent context will\\nhave 3 different perf_event_pmu_contexts. On inheritance, child ctx will\\ninsert the perf_event_pmu_context in another order and the warning will\\ntrigger.\\n\\n[ mingo: Tidied up the changelog. ]\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: perf/core: Ordenar la lista de PMU para corregir la advertencia sobre pmu_ctx_list desordenada Syskaller activa una advertencia debido a prev_epc-\u0026gt;pmu != next_epc-\u0026gt;pmu en perf_event_swap_task_ctx_data(). vmcore muestra que dos listas tienen el mismo perf_event_pmu_context, pero no en el mismo orden. El problema es que el orden de pmu_ctx_list para el padre se ve afectado por el momento en que se agrega un evento/PMU. Mientras que el orden para un hijo se ve afectado por el orden de los eventos en pinned_groups y flexible_groups. Por lo tanto, el orden de pmu_ctx_list en el padre y el hijo puede ser diferente. Para corregir este problema, inserte perf_event_pmu_context en su lugar correcto despu\u00e9s de la iteraci\u00f3n de pmu_ctx_list. El siguiente caso de prueba puede activar la advertencia anterior: # perf record -e cycles --call-graph lbr -- tasket -c 3 ./a.out \u0026amp; # perf stat -e cpu-clock,cs -p xxx // xxx es el pid de a.out test.c void main() { int count = 0; pid_t pid; printf(\\\"%d en ejecuci\u00f3n\\\\n\\\", getpid()); sleep(30); printf(\\\"en ejecuci\u00f3n\\\\n\\\"); pid = fork(); if (pid == -1) { printf(\\\"fork error\\\\n\\\"); return; } if (pid == 0) { while (1) { count++; } } else { while (1) { count++; } } } El caso de prueba primero abre un evento LBR, por lo que asignar\u00e1 task_ctx_data y luego abrir\u00e1 los eventos de tracepoint y software, por lo que el contexto principal tendr\u00e1 3 perf_event_pmu_contexts diferentes. En caso de herencia, el ctx secundario insertar\u00e1 perf_event_pmu_context en otro orden y se activar\u00e1 la advertencia. 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    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-06-30T10:28:54+00:00",
      "cve": "CVE-2025-21895",
      "id": "CVE-2025-21895",
      "initial_release_date": "2025-04-01T00:00:00+00:00",
      "product_status:known_affected": "226",
      "product_status:known_not_affected": "48",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: perf/core: Order the PMU list to fix warning about unordered pmu_ctx_list",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21895.json",
      "version": "3"
    }
  }
}



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