FKIE_CVE-2026-23127

Vulnerability from fkie_nvd - Published: 2026-02-14 15:16 - Updated: 2026-02-18 17:52
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: perf: Fix refcount warning on event->mmap_count increment When calling refcount_inc(&event->mmap_count) inside perf_mmap_rb(), the following warning is triggered: refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:25 PoC: struct perf_event_attr attr = {0}; int fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0); mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); int victim = syscall(__NR_perf_event_open, &attr, 0, -1, fd, PERF_FLAG_FD_OUTPUT); mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, victim, 0); This occurs when creating a group member event with the flag PERF_FLAG_FD_OUTPUT. The group leader should be mmap-ed and then mmap-ing the event triggers the warning. Since the event has copied the output_event in perf_event_set_output(), event->rb is set. As a result, perf_mmap_rb() calls refcount_inc(&event->mmap_count) when event->mmap_count = 0. Disallow the case when event->mmap_count = 0. This also prevents two events from updating the same user_page.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/23c0e4bd93d0b250775162faf456470485ac9fc7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d06bf78e55d5159c1b00072e606ab924ffbbad35
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf: Fix refcount warning on event-\u003emmap_count increment\n\nWhen calling refcount_inc(\u0026event-\u003emmap_count) inside perf_mmap_rb(), the\nfollowing warning is triggered:\n\n        refcount_t: addition on 0; use-after-free.\n        WARNING: lib/refcount.c:25\n\nPoC:\n\n    struct perf_event_attr attr = {0};\n    int fd = syscall(__NR_perf_event_open, \u0026attr, 0, -1, -1, 0);\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);\n    int victim = syscall(__NR_perf_event_open, \u0026attr, 0, -1, fd,\n                         PERF_FLAG_FD_OUTPUT);\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, victim, 0);\n\nThis occurs when creating a group member event with the flag\nPERF_FLAG_FD_OUTPUT. The group leader should be mmap-ed and then mmap-ing\nthe event triggers the warning.\n\nSince the event has copied the output_event in perf_event_set_output(),\nevent-\u003erb is set. As a result, perf_mmap_rb() calls\nrefcount_inc(\u0026event-\u003emmap_count) when event-\u003emmap_count = 0.\n\nDisallow the case when event-\u003emmap_count = 0. This also prevents two\nevents from updating the same user_page."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nperf: Correcci\u00f3n de la advertencia de refcount en el incremento de event-\u0026gt;mmap_count\n\nAl llamar a refcount_inc(\u0026amp;event-\u0026gt;mmap_count) dentro de perf_mmap_rb(), se activa la siguiente advertencia:\n\n        refcount_t: adici\u00f3n en 0; uso despu\u00e9s de liberaci\u00f3n.\n        ADVERTENCIA: lib/refcount.c:25\n\nPoC:\n\n    struct perf_event_attr attr = {0};\n    int fd = syscall(__NR_perf_event_open, \u0026amp;attr, 0, -1, -1, 0);\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);\n    int victim = syscall(__NR_perf_event_open, \u0026amp;attr, 0, -1, fd,\n                         PERF_FLAG_FD_OUTPUT);\n    mmap(NULL, 0x3000, PROT_READ | PROT_WRITE, MAP_SHARED, victim, 0);\n\nEsto ocurre al crear un evento miembro de grupo con la bandera PERF_FLAG_FD_OUTPUT. El l\u00edder del grupo debe ser mapeado con mmap y luego mapear el evento con mmap activa la advertencia.\n\nDado que el evento ha copiado el output_event en perf_event_set_output(), event-\u0026gt;rb est\u00e1 establecido. Como resultado, perf_mmap_rb() llama a refcount_inc(\u0026amp;event-\u0026gt;mmap_count) cuando event-\u0026gt;mmap_count = 0.\n\nNo permitir el caso cuando event-\u0026gt;mmap_count = 0. Esto tambi\u00e9n evita que dos eventos actualicen la misma user_page."
    }
  ],
  "id": "CVE-2026-23127",
  "lastModified": "2026-02-18T17:52:44.520",
  "metrics": {},
  "published": "2026-02-14T15:16:07.963",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/23c0e4bd93d0b250775162faf456470485ac9fc7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d06bf78e55d5159c1b00072e606ab924ffbbad35"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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