一、 漏洞 CVE-2025-21702 基础信息
漏洞标题
pfifo_tail_enqueue: 当sch->limit == 0时丢弃新数据包
来源：AIGC 神龙大模型
漏洞描述信息
N/A
来源：AIGC 神龙大模型
CVSS信息
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
来源：AIGC 神龙大模型
漏洞类别
未加控制的资源消耗(资源穷尽)
来源：AIGC 神龙大模型
漏洞标题
pfifo_tail_enqueue: Drop new packet when sch->limit == 0
来源：美国国家漏洞数据库 NVD
漏洞描述信息
In the Linux kernel, the following vulnerability has been resolved: pfifo_tail_enqueue: Drop new packet when sch->limit == 0 Expected behaviour: In case we reach scheduler's limit, pfifo_tail_enqueue() will drop a packet in scheduler's queue and decrease scheduler's qlen by one. Then, pfifo_tail_enqueue() enqueue new packet and increase scheduler's qlen by one. Finally, pfifo_tail_enqueue() return `NET_XMIT_CN` status code. Weird behaviour: In case we set `sch->limit == 0` and trigger pfifo_tail_enqueue() on a scheduler that has no packet, the 'drop a packet' step will do nothing. This means the scheduler's qlen still has value equal 0. Then, we continue to enqueue new packet and increase scheduler's qlen by one. In summary, we can leverage pfifo_tail_enqueue() to increase qlen by one and return `NET_XMIT_CN` status code. The problem is: Let's say we have two qdiscs: Qdisc_A and Qdisc_B. - Qdisc_A's type must have '->graft()' function to create parent/child relationship. Let's say Qdisc_A's type is `hfsc`. Enqueue packet to this qdisc will trigger `hfsc_enqueue`. - Qdisc_B's type is pfifo_head_drop. Enqueue packet to this qdisc will trigger `pfifo_tail_enqueue`. - Qdisc_B is configured to have `sch->limit == 0`. - Qdisc_A is configured to route the enqueued's packet to Qdisc_B. Enqueue packet through Qdisc_A will lead to: - hfsc_enqueue(Qdisc_A) -> pfifo_tail_enqueue(Qdisc_B) - Qdisc_B->q.qlen += 1 - pfifo_tail_enqueue() return `NET_XMIT_CN` - hfsc_enqueue() check for `NET_XMIT_SUCCESS` and see `NET_XMIT_CN` => hfsc_enqueue() don't increase qlen of Qdisc_A. The whole process lead to a situation where Qdisc_A->q.qlen == 0 and Qdisc_B->q.qlen == 1. Replace 'hfsc' with other type (for example: 'drr') still lead to the same problem. This violate the design where parent's qlen should equal to the sum of its childrens'qlen. Bug impact: This issue can be used for user->kernel privilege escalation when it is reachable.
来源：美国国家漏洞数据库 NVD
CVSS信息
N/A
来源：美国国家漏洞数据库 NVD
漏洞类别
N/A
来源：美国国家漏洞数据库 NVD
二、漏洞 CVE-2025-21702 的公开POC
# POC 描述 源链接 神龙链接
三、漏洞 CVE-2025-21702 的情报信息

  • 标题： pfifo_tail_enqueue: Drop new packet when sch->limit == 0 - kernel/git/stable/linux.git - Linux kernel stable tree -- 🔗来源链接

    标签：

    pfifo_tail_enqueue: Drop new packet when sch->limit == 0 - kernel/git/stable/linux.git - Linux kernel stable tree

  • 标题： pfifo_tail_enqueue: Drop new packet when sch->limit == 0 - kernel/git/stable/linux.git - Linux kernel stable tree -- 🔗来源链接

    标签：

    pfifo_tail_enqueue: Drop new packet when sch->limit == 0 - kernel/git/stable/linux.git - Linux kernel stable tree

  • 标题： pfifo_tail_enqueue: Drop new packet when sch->limit == 0 - kernel/git/stable/linux.git - Linux kernel stable tree -- 🔗来源链接

    标签：

    pfifo_tail_enqueue: Drop new packet when sch->limit == 0 - kernel/git/stable/linux.git - Linux kernel stable tree
  • https://nvd.nist.gov/vuln/detail/CVE-2025-21702