GHSA-PW8P-Q2M4-9CH4

Vulnerability from github – Published: 2025-02-27 03:34 – Updated: 2025-11-03 21:33
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt

If an AX25 device is bound to a socket by setting the SO_BINDTODEVICE socket option, a refcount leak will occur in ax25_release().

Commit 9fd75b66b8f6 ("ax25: Fix refcount leaks caused by ax25_cb_del()") added decrement of device refcounts in ax25_release(). In order for that to work correctly the refcounts must already be incremented when the device is bound to the socket. An AX25 device can be bound to a socket by either calling ax25_bind() or setting SO_BINDTODEVICE socket option. In both cases the refcounts should be incremented, but in fact it is done only in ax25_bind().

This bug leads to the following issue reported by Syzkaller:

================================================================ refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 1 PID: 5932 at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31 Modules linked in: CPU: 1 UID: 0 PID: 5932 Comm: syz-executor424 Not tainted 6.13.0-rc4-syzkaller-00110-g4099a71718b0 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31 Call Trace: __refcount_dec include/linux/refcount.h:336 [inline] refcount_dec include/linux/refcount.h:351 [inline] ref_tracker_free+0x710/0x820 lib/ref_tracker.c:236 netdev_tracker_free include/linux/netdevice.h:4156 [inline] netdev_put include/linux/netdevice.h:4173 [inline] netdev_put include/linux/netdevice.h:4169 [inline] ax25_release+0x33f/0xa10 net/ax25/af_ax25.c:1069 __sock_release+0xb0/0x270 net/socket.c:640 sock_close+0x1c/0x30 net/socket.c:1408 ... do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f ... ================================================================

Fix the implementation of ax25_setsockopt() by adding increment of refcounts for the new device bound, and decrement of refcounts for the old unbound device.

Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2025-21792"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-02-27T03:15:20Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt\n\nIf an AX25 device is bound to a socket by setting the SO_BINDTODEVICE\nsocket option, a refcount leak will occur in ax25_release().\n\nCommit 9fd75b66b8f6 (\"ax25: Fix refcount leaks caused by ax25_cb_del()\")\nadded decrement of device refcounts in ax25_release(). In order for that\nto work correctly the refcounts must already be incremented when the\ndevice is bound to the socket. An AX25 device can be bound to a socket\nby either calling ax25_bind() or setting SO_BINDTODEVICE socket option.\nIn both cases the refcounts should be incremented, but in fact it is done\nonly in ax25_bind().\n\nThis bug leads to the following issue reported by Syzkaller:\n\n================================================================\nrefcount_t: decrement hit 0; leaking memory.\nWARNING: CPU: 1 PID: 5932 at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31\nModules linked in:\nCPU: 1 UID: 0 PID: 5932 Comm: syz-executor424 Not tainted 6.13.0-rc4-syzkaller-00110-g4099a71718b0 #0\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\nRIP: 0010:refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31\nCall Trace:\n \u003cTASK\u003e\n __refcount_dec include/linux/refcount.h:336 [inline]\n refcount_dec include/linux/refcount.h:351 [inline]\n ref_tracker_free+0x710/0x820 lib/ref_tracker.c:236\n netdev_tracker_free include/linux/netdevice.h:4156 [inline]\n netdev_put include/linux/netdevice.h:4173 [inline]\n netdev_put include/linux/netdevice.h:4169 [inline]\n ax25_release+0x33f/0xa10 net/ax25/af_ax25.c:1069\n __sock_release+0xb0/0x270 net/socket.c:640\n sock_close+0x1c/0x30 net/socket.c:1408\n ...\n do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n ...\n \u003c/TASK\u003e\n================================================================\n\nFix the implementation of ax25_setsockopt() by adding increment of\nrefcounts for the new device bound, and decrement of refcounts for\nthe old unbound device.",
  "id": "GHSA-pw8p-q2m4-9ch4",
  "modified": "2025-11-03T21:33:01Z",
  "published": "2025-02-27T03:34:07Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21792"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/470bda72fda0fcf54300466d70ce2de62f7835d2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/90056ece99966182dc0e367f3fd2afab46ada847"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/94a0de224ed52eb2ecd4f4cb1b937b674c9fb955"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b58f7ca86a7b8e480c06e30c5163c5d2f4e24023"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bca0902e61731a75fc4860c8720168d9f1bae3b6"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html"
    }
  ],
  "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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