CVE-2025-68768 (GCVE-0-2025-68768)

Vulnerability from cvelistv5 – Published: 2026-01-13 15:28 – Updated: 2026-02-09 08:33
VLAI?
Title
inet: frags: flush pending skbs in fqdir_pre_exit()
Summary
In the Linux kernel, the following vulnerability has been resolved: inet: frags: flush pending skbs in fqdir_pre_exit() We have been seeing occasional deadlocks on pernet_ops_rwsem since September in NIPA. The stuck task was usually modprobe (often loading a driver like ipvlan), trying to take the lock as a Writer. lockdep does not track readers for rwsems so the read wasn't obvious from the reports. On closer inspection the Reader holding the lock was conntrack looping forever in nf_conntrack_cleanup_net_list(). Based on past experience with occasional NIPA crashes I looked thru the tests which run before the crash and noticed that the crash follows ip_defrag.sh. An immediate red flag. Scouring thru (de)fragmentation queues reveals skbs sitting around, holding conntrack references. The problem is that since conntrack depends on nf_defrag_ipv6, nf_defrag_ipv6 will load first. Since nf_defrag_ipv6 loads first its netns exit hooks run _after_ conntrack's netns exit hook. Flush all fragment queue SKBs during fqdir_pre_exit() to release conntrack references before conntrack cleanup runs. Also flush the queues in timer expiry handlers when they discover fqdir->dead is set, in case packet sneaks in while we're running the pre_exit flush. The commit under Fixes is not exactly the culprit, but I think previously the timer firing would eventually unblock the spinning conntrack.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db , < c70df25214ac9b32b53e18e6ae3b8f073ffa6903 (git)
Affected: d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db , < 006a5035b495dec008805df249f92c22c89c3d2e (git)
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    Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 6.18.3 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/inet_frag.h",
            "include/net/ipv6_frag.h",
            "net/ipv4/inet_fragment.c",
            "net/ipv4/ip_fragment.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "versions": [
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              "versionType": "git"
            }
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          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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            "net/ipv4/ip_fragment.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "5.3"
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              "lessThan": "5.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "6.18.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.19",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.3",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
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        }
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ninet: frags: flush pending skbs in fqdir_pre_exit()\n\nWe have been seeing occasional deadlocks on pernet_ops_rwsem since\nSeptember in NIPA. The stuck task was usually modprobe (often loading\na driver like ipvlan), trying to take the lock as a Writer.\nlockdep does not track readers for rwsems so the read wasn\u0027t obvious\nfrom the reports.\n\nOn closer inspection the Reader holding the lock was conntrack looping\nforever in nf_conntrack_cleanup_net_list(). Based on past experience\nwith occasional NIPA crashes I looked thru the tests which run before\nthe crash and noticed that the crash follows ip_defrag.sh. An immediate\nred flag. Scouring thru (de)fragmentation queues reveals skbs sitting\naround, holding conntrack references.\n\nThe problem is that since conntrack depends on nf_defrag_ipv6,\nnf_defrag_ipv6 will load first. Since nf_defrag_ipv6 loads first its\nnetns exit hooks run _after_ conntrack\u0027s netns exit hook.\n\nFlush all fragment queue SKBs during fqdir_pre_exit() to release\nconntrack references before conntrack cleanup runs. Also flush\nthe queues in timer expiry handlers when they discover fqdir-\u003edead\nis set, in case packet sneaks in while we\u0027re running the pre_exit\nflush.\n\nThe commit under Fixes is not exactly the culprit, but I think\npreviously the timer firing would eventually unblock the spinning\nconntrack."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-09T08:33:13.157Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/c70df25214ac9b32b53e18e6ae3b8f073ffa6903"
        },
        {
          "url": "https://git.kernel.org/stable/c/006a5035b495dec008805df249f92c22c89c3d2e"
        }
      ],
      "title": "inet: frags: flush pending skbs in fqdir_pre_exit()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-68768",
    "datePublished": "2026-01-13T15:28:47.106Z",
    "dateReserved": "2025-12-24T10:30:51.034Z",
    "dateUpdated": "2026-02-09T08:33:13.157Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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