CVE-2025-21895
Full vulnerability record from the local CVENow database.
Description
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
MEDIUM
CVSS score
4.7
(v3.1)
Vulnerability status
Analyzed
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-04-01 16:15:19.883000
Last modified
2026-11-05 21:17:45.450000
View original CVE JSON
{
"id": "CVE-2025-21895",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-04-01T16:15:19.883",
"lastModified": "2026-11-05T21:17:45.450",
"vulnStatus": "Analyzed",
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{
"lang": "en",
"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->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. ]"
},
{
"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->pmu != next_epc->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 después de la iteración 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 & # 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 ejecución\\n\", getpid()); sleep(30); printf(\"en ejecución\\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 asignará task_ctx_data y luego abrirá los eventos de tracepoint y software, por lo que el contexto principal tendrá 3 perf_event_pmu_contexts diferentes. En caso de herencia, el ctx secundario insertará perf_event_pmu_context en otro orden y se activará la advertencia. [mingo: Se ordenó el registro de cambios.]"
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