{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-21652",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-21652"
  ],
  "published": "2025-01-19T10:18:03Z",
  "summary": "ipvlan: Fix use-after-free in ipvlan_get_iflink().",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipvlan: Fix use-after-free in ipvlan_get_iflink().\n\nsyzbot presented an use-after-free report [0] regarding ipvlan and\nlinkwatch.\n\nipvlan does not hold a refcnt of the lower device unlike vlan and\nmacvlan.\n\nIf the linkwatch work is triggered for the ipvlan dev, the lower dev\nmight have already been freed, resulting in UAF of ipvlan->phy_dev in\nipvlan_get_iflink().\n\nWe can delay the lower dev unregistration like vlan and macvlan by\nholding the lower dev's refcnt in dev->netdev_ops->ndo_init() and\nreleasing it in dev->priv_destructor().\n\nJakub pointed out calling .ndo_XXX after unregister_netdevice() has\nreturned is error prone and suggested [1] addressing this UAF in the\ncore by taking commit 750e51603395 (\"net: avoid potential UAF in\ndefault_operstate()\") further.\n\nLet's assume unregistering devices DOWN and use RCU protection in\ndefault_operstate() not to race with the device unregistration.\n\n[0]:\nBUG: KASAN: slab-use-after-free in ipvlan_get_iflink+0x84/0x88 drivers/net/ipvlan/ipvlan_main.c:353\nRead of size 4 at addr ffff0000d768c0e0 by task kworker/u8:35/6944\n\nCPU: 0 UID: 0 PID: 6944 Comm: kworker/u8:35 Not tainted 6.13.0-rc2-g9bc5c9515b48 #12 4c3cb9e8b4565456f6a355f312ff91f4f29b3c47\nHardware name: linux,dummy-virt (DT)\nWorkqueue: events_unbound linkwatch_event\nCall trace:\n show_stack+0x38/0x50 arch/arm64/kernel/stacktrace.c:484 (C)\n __dump_stack lib/dump_stack.c:94 [inline]\n dump_stack_lvl+0xbc/0x108 lib/dump_stack.c:120\n print_address_description mm/kasan/report.c:378 [inline]\n print_report+0x16c/0x6f0 mm/kasan/report.c:489\n kasan_report+0xc0/0x120 mm/kasan/report.c:602\n __asan_report_load4_noabort+0x20/0x30 mm/kasan/report_generic.c:380\n ipvlan_get_iflink+0x84/0x88 drivers/net/ipvlan/ipvlan_main.c:353\n dev_get_iflink+0x7c/0xd8 net/core/dev.c:674\n default_operstate net/core/link_watch.c:45 [inline]\n rfc2863_policy+0x144/0x360 net/core/link_watch.c:72\n linkwatch_do_dev+0x60/0x228 net/core/link_watch.c:175\n __linkwatch_run_queue+0x2f4/0x5b8 net/core/link_watch.c:239\n linkwatch_event+0x64/0xa8 net/core/link_watch.c:282\n process_one_work+0x700/0x1398 kernel/workqueue.c:3229\n process_scheduled_works kernel/workqueue.c:3310 [inline]\n worker_thread+0x8c4/0xe10 kernel/workqueue.c:3391\n kthread+0x2b0/0x360 kernel/kthread.c:389\n ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:862\n\nAllocated by task 9303:\n kasan_save_stack mm/kasan/common.c:47 [inline]\n kasan_save_track+0x30/0x68 mm/kasan/common.c:68\n kasan_save_alloc_info+0x44/0x58 mm/kasan/generic.c:568\n poison_kmalloc_redzone mm/kasan/common.c:377 [inline]\n __kasan_kmalloc+0x84/0xa0 mm/kasan/common.c:394\n kasan_kmalloc include/linux/kasan.h:260 [inline]\n __do_kmalloc_node mm/slub.c:4283 [inline]\n __kmalloc_node_noprof+0x2a0/0x560 mm/slub.c:4289\n __kvmalloc_node_noprof+0x9c/0x230 mm/util.c:650\n alloc_netdev_mqs+0xb4/0x1118 net/core/dev.c:11209\n rtnl_create_link+0x2b8/0xb60 net/core/rtnetlink.c:3595\n rtnl_newlink_create+0x19c/0x868 net/core/rtnetlink.c:3771\n __rtnl_newlink net/core/rtnetlink.c:3896 [inline]\n rtnl_newlink+0x122c/0x15c0 net/core/rtnetlink.c:4011\n rtnetlink_rcv_msg+0x61c/0x918 net/core/rtnetlink.c:6901\n netlink_rcv_skb+0x1dc/0x398 net/netlink/af_netlink.c:2542\n rtnetlink_rcv+0x34/0x50 net/core/rtnetlink.c:6928\n netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]\n netlink_unicast+0x618/0x838 net/netlink/af_netlink.c:1347\n netlink_sendmsg+0x5fc/0x8b0 net/netlink/af_netlink.c:1891\n sock_sendmsg_nosec net/socket.c:711 [inline]\n __sock_sendmsg net/socket.c:726 [inline]\n __sys_sendto+0x2ec/0x438 net/socket.c:2197\n __do_sys_sendto net/socket.c:2204 [inline]\n __se_sys_sendto net/socket.c:2200 [inline]\n __arm64_sys_sendto+0xe4/0x110 net/socket.c:2200\n __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]\n invoke_syscall+0x90/0x278 arch/arm64/kernel/syscall.c:49\n el0_svc_common+0x13c/0x250 arch/arm64/kernel/syscall.c:132\n do_el0_svc+0x54/0x70 arch/arm64/kernel/syscall.c:151\n el\n---truncated---",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
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        "name": "linux"
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  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-21652"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ba9f7c16ec879c83bb4f80406773a911aace8267"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/52a24538d569f48e79d1a169a5d359d384152950"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/cb358ff94154774d031159b018adf45e17673941"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerability is reached through rtnetlink (`RTM_NEWLINK`/`RTM_DELLINK`) on an AF_NETLINK socket, requiring local system access to issue the syscalls that create and tear down the ipvlan and its lower device. No remote packet processing is involved.\nAC:L - The attacker controls both sides of the race \u2014 creating a carrier-down veth plus ipvlan deterministically arms the vulnerable `!netif_carrier_ok()` branch in `default_operstate()`, and the teardown that frees the lower device is issued by the attacker in a tight loop against the linkwatch worker. No condition depends on external state, and syzkaller reproduced it.\nPR:L - The rtnetlink path is gated only by `netlink_net_capable(skb, CAP_NET_ADMIN)` over the netns's owning user namespace, so any unprivileged local user obtains it with `unshare -Urn` and can then create veth and ipvlan devices freely. No real root in the initial namespace is needed.\nUI:N - The attacker performs every step \u2014 device creation, bring-up, and deletion \u2014 from their own process; no victim action or cooperation is required.\nS:U - The corruption and its consequences are confined to kernel memory within the same security authority; this is standard kernel-level memory unsafety with no VM, IOMMU, or hypervisor boundary crossed.\nC:H - The dangling `ipvlan->phy_dev` yields a use-after-free read from a freed 4096-byte `kmalloc-cg` netdev object that the attacker can reallocate and groom with controlled content, and the resulting value propagates into an `__dev_get_by_index()` lookup whose outcome is observable via `IFLA_OPERSTATE`/sysfs, giving an attacker-influenced kernel read channel.\nI:H - This is a full netdev-lifetime use-after-free on a stale `struct net_device` pointer in a sprayable general-purpose slab cache, which is the classic basis for heap grooming and type-confusion primitives leading to kernel state modification and control-flow hijacking.\nA:H - The bug produces a KASAN slab-use-after-free with a resulting oops, and because the netdev is `kvmalloc`'d the freed region can be unmapped, turning the dereference into a kernel panic; the attacker can retrigger it repeatedly."
    }
  }
}