nvd-json-data-feeds/CVE-2022/CVE-2022-490xx/CVE-2022-49006.json

{
  "id": "CVE-2022-49006",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2024-10-21T20:15:12.103",
  "lastModified": "2024-10-21T20:15:12.103",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Free buffers when a used dynamic event is removed\n\nAfter 65536 dynamic events have been added and removed, the \"type\" field\nof the event then uses the first type number that is available (not\ncurrently used by other events). A type number is the identifier of the\nbinary blobs in the tracing ring buffer (known as events) to map them to\nlogic that can parse the binary blob.\n\nThe issue is that if a dynamic event (like a kprobe event) is traced and\nis in the ring buffer, and then that event is removed (because it is\ndynamic, which means it can be created and destroyed), if another dynamic\nevent is created that has the same number that new event's logic on\nparsing the binary blob will be used.\n\nTo show how this can be an issue, the following can crash the kernel:\n\n # cd /sys/kernel/tracing\n # for i in `seq 65536`; do\n     echo 'p:kprobes/foo do_sys_openat2 $arg1:u32' > kprobe_events\n # done\n\nFor every iteration of the above, the writing to the kprobe_events will\nremove the old event and create a new one (with the same format) and\nincrease the type number to the next available on until the type number\nreaches over 65535 which is the max number for the 16 bit type. After it\nreaches that number, the logic to allocate a new number simply looks for\nthe next available number. When an dynamic event is removed, that number\nis then available to be reused by the next dynamic event created. That is,\nonce the above reaches the max number, the number assigned to the event in\nthat loop will remain the same.\n\nNow that means deleting one dynamic event and created another will reuse\nthe previous events type number. This is where bad things can happen.\nAfter the above loop finishes, the kprobes/foo event which reads the\ndo_sys_openat2 function call's first parameter as an integer.\n\n # echo 1 > kprobes/foo/enable\n # cat /etc/passwd > /dev/null\n # cat trace\n             cat-2211    [005] ....  2007.849603: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196\n             cat-2211    [005] ....  2007.849620: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196\n             cat-2211    [005] ....  2007.849838: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196\n             cat-2211    [005] ....  2007.849880: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196\n # echo 0 > kprobes/foo/enable\n\nNow if we delete the kprobe and create a new one that reads a string:\n\n # echo 'p:kprobes/foo do_sys_openat2 +0($arg2):string' > kprobe_events\n\nAnd now we can the trace:\n\n # cat trace\n        sendmail-1942    [002] .....   530.136320: foo: (do_sys_openat2+0x0/0x240) arg1=             cat-2046    [004] .....   530.930817: foo: (do_sys_openat2+0x0/0x240) arg1=\"\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\"\n             cat-2046    [004] .....   530.930961: foo: (do_sys_openat2+0x0/0x240) arg1=\"\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\ufffd\"\n             cat-2046    [004] .....   530.9
    }
  ],
  "metrics": {},
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/1603feac154ff38514e8354e3079a455eb4801e2",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/417d5ea6e735e5d88ffb6c436cf2938f3f476dd1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4313e5a613049dfc1819a6dfb5f94cf2caff9452",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/be111ebd8868d4b7c041cb3c6102e1ae27d6dc1d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/c52d0c8c4f38f7580cff61c4dfe1034c580cedfd",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}