{"cve":"CVE-2025-21895","nvd":{"published":"2025-04-01T16:15:19.883","modified":"2026-06-17T08:44:33.203","status":"Analyzed","description":"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->pmu != next_epc->pmu 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. ]","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","score":4.7},"cwes":["CWE-362"],"references":["https://git.kernel.org/stable/c/2016066c66192a99d9e0ebf433789c490a6785a2","https://git.kernel.org/stable/c/3e812a70732d84b7873cea61a7f6349b9a9dcbf5","https://git.kernel.org/stable/c/7d582eb6e4e100959ba07083d7563453c8c2a343","https://git.kernel.org/stable/c/f0c3971405cef6892844016aa710121a02da3a23"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:00:28.034033815+00:00"},"epss":{"cve":"CVE-2025-21895","score":0.00148,"percentile":0.03975,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}