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

Vulnerability from cvelistv5 – Published: 2026-01-13 15:28 – Updated: 2026-06-19 11:57
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 , < 22ee4010866da81aeee08e1ea3fddbe418feb212 (git)
Affected: d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db , < 543555954b1ee8d1903a7020324efb41b0c97428 (git)
Affected: d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db , < c70df25214ac9b32b53e18e6ae3b8f073ffa6903 (git)
Affected: d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db , < 006a5035b495dec008805df249f92c22c89c3d2e (git)
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Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.3 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
            "include/net/inet_frag.h",
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          "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."
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        "dateUpdated": "2026-06-19T11:57:29.047Z",
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        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/006a5035b495dec008805df249f92c22c89c3d2e"
        }
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    "cveId": "CVE-2025-68768",
    "datePublished": "2026-01-13T15:28:47.106Z",
    "dateReserved": "2025-12-24T10:30:51.034Z",
    "dateUpdated": "2026-06-19T11:57:29.047Z",
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}



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