{"id":"CVE-2025-21895","summary":"perf/core: Order the PMU list to fix warning about unordered pmu_ctx_list","details":"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 &\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. ]","modified":"2026-04-02T12:45:16.521562Z","published":"2025-04-01T15:26:48.607Z","related":["SUSE-SU-2025:01614-1","SUSE-SU-2025:01707-1","SUSE-SU-2025:01919-1","SUSE-SU-2025:01951-1","SUSE-SU-2025:01964-1","SUSE-SU-2025:01967-1","SUSE-SU-2025:20192-1","SUSE-SU-2025:20206-1","SUSE-SU-2025:20270-1","SUSE-SU-2025:20283-1","USN-7521-2"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21895.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2016066c66192a99d9e0ebf433789c490a6785a2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3e812a70732d84b7873cea61a7f6349b9a9dcbf5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7d582eb6e4e100959ba07083d7563453c8c2a343"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f0c3971405cef6892844016aa710121a02da3a23"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21895.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21895"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"bd27568117664b8b3e259721393df420ed51f57b"},{"fixed":"f0c3971405cef6892844016aa710121a02da3a23"},{"fixed":"7d582eb6e4e100959ba07083d7563453c8c2a343"},{"fixed":"3e812a70732d84b7873cea61a7f6349b9a9dcbf5"},{"fixed":"2016066c66192a99d9e0ebf433789c490a6785a2"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21895.json"}}],"schema_version":"1.7.5"}