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CVE-2025-39925

Full vulnerability record from the local CVENow database.

Description

In 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]

Severity
MEDIUM
CVSS score
5.5 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-10-01 08:15:35.857000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON 
{
  "id": "CVE-2025-39925",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-10-01T08:15:35.857",
  "lastModified": "2026-10-19T21:10:00.160",
  "vulnStatus": "Modified",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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]"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ncan: j1939: implementar gestor de notificación NETDEV_UNREGISTER\n\nsyzbot está reportando\n\n  unregister_netdevice: waiting for vcan0 to become free. Usage count = 2\n\nproblema, porque el protocolo j1939 no tenía un gestor de notificación NETDEV_UNREGISTER para deshacer los cambios realizados por j1939_sk_bind().\n\nEl commit 25fe97cb7620 ('can: j1939: mover j1939_priv_put() al callback sk_destruct') espera que una llamada a j1939_priv_put() pueda retrasarse incondicionalmente hasta que se llame a j1939_sk_sock_destruct(). Pero necesitamos llamar a j1939_priv_put() contra una referencia extra mantenida por la llamada a j1939_sk_bind() (como parte de deshacer los cambios realizados por j1939_sk_bind()) tan pronto como se active la notificación NETDEV_UNREGISTER (es decir, antes de que se llame a j1939_sk_sock_destruct() a través de j1939_sk_release()). De lo contrario, la referencia extra en 'struct j1939_priv' mantenida por la llamada a j1939_sk_bind() impide que 'struct net_device' reduzca el contador de uso a 1; haciendo imposible que unregister_netdevice() continúe.\n\n[mkl: remove space in front of label]"
    }
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              "versionType": "original_commit_for_fix",
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          "role": "CISA Coordinator",
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