GHSA-G35J-5V93-P28M
Vulnerability from github – Published: 2025-10-01 09:30 – Updated: 2026-09-02 15:33In the Linux kernel, the following vulnerability has been resolved:
can: j1939: implement NETDEV_UNREGISTER notification handler
syzbot is reporting
unregister_netdevice: waiting for vcan0 to become free. Usage count = 2
problem, for j1939 protocol did not have NETDEV_UNREGISTER notification handler for undoing changes made by j1939_sk_bind().
Commit 25fe97cb7620 ("can: j1939: move j1939_priv_put() into sk_destruct callback") expects that a call to j1939_priv_put() can be unconditionally delayed until j1939_sk_sock_destruct() is called. But we need to call j1939_priv_put() against an extra ref held by j1939_sk_bind() call (as a part of undoing changes made by j1939_sk_bind()) as soon as NETDEV_UNREGISTER notification fires (i.e. before j1939_sk_sock_destruct() is called via j1939_sk_release()). Otherwise, the extra ref on "struct j1939_priv" held by j1939_sk_bind() call prevents "struct net_device" from dropping the usage count to 1; making it impossible for unregister_netdevice() to continue.
[mkl: remove space in front of label]
{
"affected": [],
"aliases": [
"CVE-2025-39925"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-10-01T08:15:35Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncan: j1939: implement NETDEV_UNREGISTER notification handler\n\nsyzbot is reporting\n\n unregister_netdevice: waiting for vcan0 to become free. Usage count = 2\n\nproblem, for j1939 protocol did not have NETDEV_UNREGISTER notification\nhandler for undoing changes made by j1939_sk_bind().\n\nCommit 25fe97cb7620 (\"can: j1939: move j1939_priv_put() into sk_destruct\ncallback\") expects that a call to j1939_priv_put() can be unconditionally\ndelayed until j1939_sk_sock_destruct() is called. But we need to call\nj1939_priv_put() against an extra ref held by j1939_sk_bind() call\n(as a part of undoing changes made by j1939_sk_bind()) as soon as\nNETDEV_UNREGISTER notification fires (i.e. before j1939_sk_sock_destruct()\nis called via j1939_sk_release()). Otherwise, the extra ref on \"struct\nj1939_priv\" held by j1939_sk_bind() call prevents \"struct net_device\" from\ndropping the usage count to 1; making it impossible for\nunregister_netdevice() to continue.\n\n[mkl: remove space in front of label]",
"id": "GHSA-g35j-5v93-p28m",
"modified": "2026-09-02T15:33:17Z",
"published": "2025-10-01T09:30:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39925"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2c88069fac2c792e228e6a4ae71c9b9b5b9a87a6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/479d8a2aedcc1db16f14c1a8a9c74b5bdf18b9ac"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4e154cb5e7681c2910e2dfa09f05e3469e333745"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/76957b618ce729c3bd1e782fbc9d9991af653925"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7fcbe5b2c6a4b5407bf2241fdb71e0a390f6ab9a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/da9e8f429139928570407e8f90559b5d46c20262"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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