ghsa-fj34-p4r2-ghh5
Vulnerability from github
Published
2024-05-21 15:31
Modified
2024-12-24 18:30
Severity ?
7.0 (High) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Details

In the Linux kernel, the following vulnerability has been resolved:

ALSA: seq: Fix race of snd_seq_timer_open()

The timer instance per queue is exclusive, and snd_seq_timer_open() should have managed the concurrent accesses. It looks as if it's checking the already existing timer instance at the beginning, but it's not right, because there is no protection, hence any later concurrent call of snd_seq_timer_open() may override the timer instance easily. This may result in UAF, as the leftover timer instance can keep running while the queue itself gets closed, as spotted by syzkaller recently.

For avoiding the race, add a proper check at the assignment of tmr->timeri again, and return -EBUSY if it's been already registered.

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{
  "affected": [],
  "aliases": [
    "CVE-2021-47281"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-05-21T15:15:16Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: Fix race of snd_seq_timer_open()\n\nThe timer instance per queue is exclusive, and snd_seq_timer_open()\nshould have managed the concurrent accesses.  It looks as if it\u0027s\nchecking the already existing timer instance at the beginning, but\nit\u0027s not right, because there is no protection, hence any later\nconcurrent call of snd_seq_timer_open() may override the timer\ninstance easily.  This may result in UAF, as the leftover timer\ninstance can keep running while the queue itself gets closed, as\nspotted by syzkaller recently.\n\nFor avoiding the race, add a proper check at the assignment of\ntmr-\u003etimeri again, and return -EBUSY if it\u0027s been already registered.",
  "id": "GHSA-fj34-p4r2-ghh5",
  "modified": "2024-12-24T18:30:48Z",
  "published": "2024-05-21T15:31:41Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47281"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/536a7646c00a0f14fee49e5e313109e5da2f6031"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/83e197a8414c0ba545e7e3916ce05f836f349273"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bd7d88b0874f82f7b29d1a53e574cedaf23166ba"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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