tun: Fix memory leak for detached NAPI queue.

{
  "id": "0bb324a9669bbb503929db68041c7cc48ee5624d1a064a9f36b26f80e2b1487b",
  "url": "https://osv.dev/vulnerability/CVE-2023-53685",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "tun: Fix memory leak for detached NAPI queue.",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: tun: Fix memory leak for detached NAPI queue. syzkaller reported [0] memory leaks of sk and skb related to the TUN device with no repro, but we can reproduce it easily with: struct ifreq ifr = {} int fd_tun, fd_tmp; char buf[4] = {}; fd_tun = openat(AT_FDCWD, \"/dev/net/tun\", O_WRONLY, 0); ifr.ifr_flags = IFF_TUN | IFF_NAPI | IFF_MULTI_QUEUE; ioctl(fd_tun, TUNSETIFF, &ifr); ifr.ifr_flags = IFF_DETACH_QUEUE; ioctl(fd_tun, TUNSETQUEUE, &ifr); fd_tmp = socket(AF_PACKET, SOCK_PACKET, 0); ifr.ifr_flags = IFF_UP; ioctl(fd_tmp, SIOCSIFFLAGS, &ifr); write(fd_tun, buf, sizeof(buf)); close(fd_tun); If we enable NAPI and multi-queue on a TUN device, we can put skb into tfile->sk.sk_write_queue after the queue is detached. We should prevent it by checking tfile->detached before queuing skb. Note this must be done under tfile->sk.sk_write_queue.lock because write() and ioctl(IFF_DETACH_QUEUE) can run concurrently. Otherwise, there would be a small race window: write() ioctl(IFF_DETACH_QUEUE) `- tun_get_user `- __tun_detach |- if (tfile->detached) |- tun_disable_queue | `-> false | `- tfile->detached = tun | `- tun_queue_purge |- spin_lock_bh(&queue->lock) `- __skb_queue_tail(queue, skb) Another solution is to call tun_queue_purge() when closing and reattaching the detached queue, but it could paper over another problems. Also, we do the same kind of test for IFF_NAPI_FRAGS. [0]: unreferenced object 0xffff88801edbc800 (size",
    "evidence": "osv:CVE-2023-53685",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.30",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.3.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2023-53685",
      "aliases": [
        "CVE-2023-53685"
      ],
      "affected": [
        {
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            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "cde8b15f1aabe327038ee4e0e11dd6b798572f69"
                },
                {
                  "fixed": "9cae243b9ae25adfe468cd47ceca591f6725b79c"
                },
                {
                  "fixed": "0d20210a190f76db9ec35ee4e0fc77e6c7a148f5"
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                {
                  "fixed": "82b2bc279467c875ec36f8ef820f00997c2a4e8e"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53685.json"
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        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "3.8.0"
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                {
                  "fixed": "6.1.30"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
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                {
                  "fixed": "6.3.4"
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53685.json"
          }
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      ],
      "modified": "2026-10-30T02:31:02.532805805Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0d20210a190f76db9ec35ee4e0fc77e6c7a148f5",
        "https://git.kernel.org/stable/c/82b2bc279467c875ec36f8ef820f00997c2a4e8e",
        "https://git.kernel.org/stable/c/9cae243b9ae25adfe468cd47ceca591f6725b79c",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/53xxx/CVE-2023-53685.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2023-53685",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/53xxx/CVE-2023-53685.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2023-53685",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 519139,
  "published_at": "2025-10-07T15:21:38.124+00:00"
}