CVE-2025-38470 (GCVE-0-2025-38470)

Vulnerability from cvelistv5 – Published: 2025-07-28 11:21 – Updated: 2025-11-03 17:38
VLAI?
Title
net: vlan: fix VLAN 0 refcount imbalance of toggling filtering during runtime
Summary
In the Linux kernel, the following vulnerability has been resolved: net: vlan: fix VLAN 0 refcount imbalance of toggling filtering during runtime Assuming the "rx-vlan-filter" feature is enabled on a net device, the 8021q module will automatically add or remove VLAN 0 when the net device is put administratively up or down, respectively. There are a couple of problems with the above scheme. The first problem is a memory leak that can happen if the "rx-vlan-filter" feature is disabled while the device is running: # ip link add bond1 up type bond mode 0 # ethtool -K bond1 rx-vlan-filter off # ip link del dev bond1 When the device is put administratively down the "rx-vlan-filter" feature is disabled, so the 8021q module will not remove VLAN 0 and the memory will be leaked [1]. Another problem that can happen is that the kernel can automatically delete VLAN 0 when the device is put administratively down despite not adding it when the device was put administratively up since during that time the "rx-vlan-filter" feature was disabled. null-ptr-unref or bug_on[2] will be triggered by unregister_vlan_dev() for refcount imbalance if toggling filtering during runtime: $ ip link add bond0 type bond mode 0 $ ip link add link bond0 name vlan0 type vlan id 0 protocol 802.1q $ ethtool -K bond0 rx-vlan-filter off $ ifconfig bond0 up $ ethtool -K bond0 rx-vlan-filter on $ ifconfig bond0 down $ ip link del vlan0 Root cause is as below: step1: add vlan0 for real_dev, such as bond, team. register_vlan_dev vlan_vid_add(real_dev,htons(ETH_P_8021Q),0) //refcnt=1 step2: disable vlan filter feature and enable real_dev step3: change filter from 0 to 1 vlan_device_event vlan_filter_push_vids ndo_vlan_rx_add_vid //No refcnt added to real_dev vlan0 step4: real_dev down vlan_device_event vlan_vid_del(dev, htons(ETH_P_8021Q), 0); //refcnt=0 vlan_info_rcu_free //free vlan0 step5: delete vlan0 unregister_vlan_dev BUG_ON(!vlan_info); //vlan_info is null Fix both problems by noting in the VLAN info whether VLAN 0 was automatically added upon NETDEV_UP and based on that decide whether it should be deleted upon NETDEV_DOWN, regardless of the state of the "rx-vlan-filter" feature. [1] unreferenced object 0xffff8880068e3100 (size 256): comm "ip", pid 384, jiffies 4296130254 hex dump (first 32 bytes): 00 20 30 0d 80 88 ff ff 00 00 00 00 00 00 00 00 . 0............. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace (crc 81ce31fa): __kmalloc_cache_noprof+0x2b5/0x340 vlan_vid_add+0x434/0x940 vlan_device_event.cold+0x75/0xa8 notifier_call_chain+0xca/0x150 __dev_notify_flags+0xe3/0x250 rtnl_configure_link+0x193/0x260 rtnl_newlink_create+0x383/0x8e0 __rtnl_newlink+0x22c/0xa40 rtnl_newlink+0x627/0xb00 rtnetlink_rcv_msg+0x6fb/0xb70 netlink_rcv_skb+0x11f/0x350 netlink_unicast+0x426/0x710 netlink_sendmsg+0x75a/0xc20 __sock_sendmsg+0xc1/0x150 ____sys_sendmsg+0x5aa/0x7b0 ___sys_sendmsg+0xfc/0x180 [2] kernel BUG at net/8021q/vlan.c:99! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 382 Comm: ip Not tainted 6.16.0-rc3 #61 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:unregister_vlan_dev (net/8021q/vlan.c:99 (discriminator 1)) RSP: 0018:ffff88810badf310 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff88810da84000 RCX: ffffffffb47ceb9a RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff88810e8b43c8 RBP: 0000000000000000 R08: 0000000000000000 R09: fffffbfff6cefe80 R10: ffffffffb677f407 R11: ffff88810badf3c0 R12: ffff88810e8b4000 R13: 0000000000000000 R14: ffff88810642a5c0 R15: 000000000000017e FS: 00007f1ff68c20c0(0000) GS:ffff888163a24000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1ff5dad240 CR3: 0000000107e56000 CR4: 00000000000006f0 Call Trace: <TASK ---truncated---
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: ad1afb00393915a51c21b1ae8704562bf036855f , < ba48d3993af23753e1f1f01c8d592de9c7785f24 (git)
Affected: ad1afb00393915a51c21b1ae8704562bf036855f , < 35142b3816832889e50164d993018ea5810955ae (git)
Affected: ad1afb00393915a51c21b1ae8704562bf036855f , < 047b61a24d7c866c502aeeea482892969a68f216 (git)
Affected: ad1afb00393915a51c21b1ae8704562bf036855f , < d43ef15bf4856c8c4c6c3572922331a5f06deb77 (git)
Affected: ad1afb00393915a51c21b1ae8704562bf036855f , < bb515c41306454937464da055609b5fb0a27821b (git)
Affected: ad1afb00393915a51c21b1ae8704562bf036855f , < 8984bcbd1edf5bee5be06ad771d157333b790c33 (git)
Affected: ad1afb00393915a51c21b1ae8704562bf036855f , < 93715aa2d80e6c5cea1bb486321fc4585076928b (git)
Affected: ad1afb00393915a51c21b1ae8704562bf036855f , < 579d4f9ca9a9a605184a9b162355f6ba131f678d (git)
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    Linux Linux Affected: 2.6.36
Unaffected: 0 , < 2.6.36 (semver)
Unaffected: 5.4.297 , ≤ 5.4.* (semver)
Unaffected: 5.10.241 , ≤ 5.10.* (semver)
Unaffected: 5.15.190 , ≤ 5.15.* (semver)
Unaffected: 6.1.147 , ≤ 6.1.* (semver)
Unaffected: 6.6.100 , ≤ 6.6.* (semver)
Unaffected: 6.12.40 , ≤ 6.12.* (semver)
Unaffected: 6.15.8 , ≤ 6.15.* (semver)
Unaffected: 6.16 , ≤ * (original_commit_for_fix)
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            "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: vlan: fix VLAN 0 refcount imbalance of toggling filtering during runtime\n\nAssuming the \"rx-vlan-filter\" feature is enabled on a net device, the\n8021q module will automatically add or remove VLAN 0 when the net device\nis put administratively up or down, respectively. There are a couple of\nproblems with the above scheme.\n\nThe first problem is a memory leak that can happen if the \"rx-vlan-filter\"\nfeature is disabled while the device is running:\n\n # ip link add bond1 up type bond mode 0\n # ethtool -K bond1 rx-vlan-filter off\n # ip link del dev bond1\n\nWhen the device is put administratively down the \"rx-vlan-filter\"\nfeature is disabled, so the 8021q module will not remove VLAN 0 and the\nmemory will be leaked [1].\n\nAnother problem that can happen is that the kernel can automatically\ndelete VLAN 0 when the device is put administratively down despite not\nadding it when the device was put administratively up since during that\ntime the \"rx-vlan-filter\" feature was disabled. null-ptr-unref or\nbug_on[2] will be triggered by unregister_vlan_dev() for refcount\nimbalance if toggling filtering during runtime:\n\n$ ip link add bond0 type bond mode 0\n$ ip link add link bond0 name vlan0 type vlan id 0 protocol 802.1q\n$ ethtool -K bond0 rx-vlan-filter off\n$ ifconfig bond0 up\n$ ethtool -K bond0 rx-vlan-filter on\n$ ifconfig bond0 down\n$ ip link del vlan0\n\nRoot cause is as below:\nstep1: add vlan0 for real_dev, such as bond, team.\nregister_vlan_dev\n    vlan_vid_add(real_dev,htons(ETH_P_8021Q),0) //refcnt=1\nstep2: disable vlan filter feature and enable real_dev\nstep3: change filter from 0 to 1\nvlan_device_event\n    vlan_filter_push_vids\n        ndo_vlan_rx_add_vid //No refcnt added to real_dev vlan0\nstep4: real_dev down\nvlan_device_event\n    vlan_vid_del(dev, htons(ETH_P_8021Q), 0); //refcnt=0\n        vlan_info_rcu_free //free vlan0\nstep5: delete vlan0\nunregister_vlan_dev\n    BUG_ON(!vlan_info); //vlan_info is null\n\nFix both problems by noting in the VLAN info whether VLAN 0 was\nautomatically added upon NETDEV_UP and based on that decide whether it\nshould be deleted upon NETDEV_DOWN, regardless of the state of the\n\"rx-vlan-filter\" feature.\n\n[1]\nunreferenced object 0xffff8880068e3100 (size 256):\n  comm \"ip\", pid 384, jiffies 4296130254\n  hex dump (first 32 bytes):\n    00 20 30 0d 80 88 ff ff 00 00 00 00 00 00 00 00  . 0.............\n    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................\n  backtrace (crc 81ce31fa):\n    __kmalloc_cache_noprof+0x2b5/0x340\n    vlan_vid_add+0x434/0x940\n    vlan_device_event.cold+0x75/0xa8\n    notifier_call_chain+0xca/0x150\n    __dev_notify_flags+0xe3/0x250\n    rtnl_configure_link+0x193/0x260\n    rtnl_newlink_create+0x383/0x8e0\n    __rtnl_newlink+0x22c/0xa40\n    rtnl_newlink+0x627/0xb00\n    rtnetlink_rcv_msg+0x6fb/0xb70\n    netlink_rcv_skb+0x11f/0x350\n    netlink_unicast+0x426/0x710\n    netlink_sendmsg+0x75a/0xc20\n    __sock_sendmsg+0xc1/0x150\n    ____sys_sendmsg+0x5aa/0x7b0\n    ___sys_sendmsg+0xfc/0x180\n\n[2]\nkernel BUG at net/8021q/vlan.c:99!\nOops: invalid opcode: 0000 [#1] SMP KASAN PTI\nCPU: 0 UID: 0 PID: 382 Comm: ip Not tainted 6.16.0-rc3 #61 PREEMPT(voluntary)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996),\nBIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014\nRIP: 0010:unregister_vlan_dev (net/8021q/vlan.c:99 (discriminator 1))\nRSP: 0018:ffff88810badf310 EFLAGS: 00010246\nRAX: 0000000000000000 RBX: ffff88810da84000 RCX: ffffffffb47ceb9a\nRDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff88810e8b43c8\nRBP: 0000000000000000 R08: 0000000000000000 R09: fffffbfff6cefe80\nR10: ffffffffb677f407 R11: ffff88810badf3c0 R12: ffff88810e8b4000\nR13: 0000000000000000 R14: ffff88810642a5c0 R15: 000000000000017e\nFS:  00007f1ff68c20c0(0000) GS:ffff888163a24000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 00007f1ff5dad240 CR3: 0000000107e56000 CR4: 00000000000006f0\nCall Trace:\n \u003cTASK\n---truncated---"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-08-28T14:43:09.081Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ba48d3993af23753e1f1f01c8d592de9c7785f24"
        },
        {
          "url": "https://git.kernel.org/stable/c/35142b3816832889e50164d993018ea5810955ae"
        },
        {
          "url": "https://git.kernel.org/stable/c/047b61a24d7c866c502aeeea482892969a68f216"
        },
        {
          "url": "https://git.kernel.org/stable/c/d43ef15bf4856c8c4c6c3572922331a5f06deb77"
        },
        {
          "url": "https://git.kernel.org/stable/c/bb515c41306454937464da055609b5fb0a27821b"
        },
        {
          "url": "https://git.kernel.org/stable/c/8984bcbd1edf5bee5be06ad771d157333b790c33"
        },
        {
          "url": "https://git.kernel.org/stable/c/93715aa2d80e6c5cea1bb486321fc4585076928b"
        },
        {
          "url": "https://git.kernel.org/stable/c/579d4f9ca9a9a605184a9b162355f6ba131f678d"
        }
      ],
      "title": "net: vlan: fix VLAN 0 refcount imbalance of toggling filtering during runtime",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-38470",
    "datePublished": "2025-07-28T11:21:32.002Z",
    "dateReserved": "2025-04-16T04:51:24.020Z",
    "dateUpdated": "2025-11-03T17:38:35.299Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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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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