CVE-2025-68325 (GCVE-0-2025-68325)
Vulnerability from cvelistv5
Published
2025-12-18 15:02
Modified
2025-12-18 15:02
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_cake: Fix incorrect qlen reduction in cake_drop In cake_drop(), qdisc_tree_reduce_backlog() is used to update the qlen and backlog of the qdisc hierarchy. Its caller, cake_enqueue(), assumes that the parent qdisc will enqueue the current packet. However, this assumption breaks when cake_enqueue() returns NET_XMIT_CN: the parent qdisc stops enqueuing current packet, leaving the tree qlen/backlog accounting inconsistent. This mismatch can lead to a NULL dereference (e.g., when the parent Qdisc is qfq_qdisc). This patch computes the qlen/backlog delta in a more robust way by observing the difference before and after the series of cake_drop() calls, and then compensates the qdisc tree accounting if cake_enqueue() returns NET_XMIT_CN. To ensure correct compensation when ACK thinning is enabled, a new variable is introduced to keep qlen unchanged.
References
Impacted products
Vendor Product Version
Linux Linux Version: ff57186b2cc39766672c4c0332323933e5faaa88
Version: 15de71d06a400f7fdc15bf377a2552b0ec437cf5
Version: 15de71d06a400f7fdc15bf377a2552b0ec437cf5
Version: 15de71d06a400f7fdc15bf377a2552b0ec437cf5
Version: 7689ab22de36f8db19095f6bdf11f28cfde92f5c
Version: de04ddd2980b48caa8d7e24a7db2742917a8b280
Version: 0dacfc5372e314d1219f03e64dde3ab495a5a25e
Version: 710866fc0a64eafcb8bacd91bcb1329eb7e5035f
Version: aa12ee1c1bd260943fd6ab556d8635811c332eeb
Version: 62d591dde4defb1333d202410609c4ddeae060b3
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_cake: Fix incorrect qlen reduction in cake_drop\n\nIn cake_drop(), qdisc_tree_reduce_backlog() is used to update the qlen\nand backlog of the qdisc hierarchy. Its caller, cake_enqueue(), assumes\nthat the parent qdisc will enqueue the current packet. However, this\nassumption breaks when cake_enqueue() returns NET_XMIT_CN: the parent\nqdisc stops enqueuing current packet, leaving the tree qlen/backlog\naccounting inconsistent. This mismatch can lead to a NULL dereference\n(e.g., when the parent Qdisc is qfq_qdisc).\n\nThis patch computes the qlen/backlog delta in a more robust way by\nobserving the difference before and after the series of cake_drop()\ncalls, and then compensates the qdisc tree accounting if cake_enqueue()\nreturns NET_XMIT_CN.\n\nTo ensure correct compensation when ACK thinning is enabled, a new\nvariable is introduced to keep qlen unchanged."
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      "providerMetadata": {
        "dateUpdated": "2025-12-18T15:02:50.214Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-68325",
    "datePublished": "2025-12-18T15:02:50.214Z",
    "dateReserved": "2025-12-16T14:48:05.296Z",
    "dateUpdated": "2025-12-18T15:02:50.214Z",
    "state": "PUBLISHED"
  },
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  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-68325\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-18T15:16:06.320\",\"lastModified\":\"2025-12-19T18:00:54.283\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet/sched: sch_cake: Fix incorrect qlen reduction in cake_drop\\n\\nIn cake_drop(), qdisc_tree_reduce_backlog() is used to update the qlen\\nand backlog of the qdisc hierarchy. Its caller, cake_enqueue(), assumes\\nthat the parent qdisc will enqueue the current packet. However, this\\nassumption breaks when cake_enqueue() returns NET_XMIT_CN: the parent\\nqdisc stops enqueuing current packet, leaving the tree qlen/backlog\\naccounting inconsistent. This mismatch can lead to a NULL dereference\\n(e.g., when the parent Qdisc is qfq_qdisc).\\n\\nThis patch computes the qlen/backlog delta in a more robust way by\\nobserving the difference before and after the series of cake_drop()\\ncalls, and then compensates the qdisc tree accounting if cake_enqueue()\\nreturns NET_XMIT_CN.\\n\\nTo ensure correct compensation when ACK thinning is enabled, a new\\nvariable is introduced to keep qlen unchanged.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0b6216f9b3d1c33c76f74511026e5de5385ee520\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/3ed6c458530a547ed0c9ea0b02b19bab620be88b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/529c284cc2815c8350860e9a31722050fe7117cb\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9fefc78f7f02d71810776fdeb119a05a946a27cc\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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