GHSA-2VFM-8XC8-7W2C
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-09-25 12:31In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_sysfs: Fix NULL pointer dereference in device_del()
A NULL pointer dereference in klist_put() occurs when a child device (such as a BNEP network device in bnep_session) is concurrently being unregistered while hci_conn_del_sysfs() reparents child devices.
This is caused by a race condition between hci_conn_del_sysfs() and concurrent child device unregistration (e.g. bnep_session calling unregister_netdev()). During device unregistration, device_del() snapshots a non-NULL parent pointer. Concurrently, hci_conn_del_sysfs() finds the child device using device_find_any_child() and calls device_move() to reparent it to NULL, which removes the node from its parent's klist and clears knode_parent. Subsequently, device_del() calls klist_del(&dev->p->knode_parent) using the stale parent snapshot, causing klist_put() to dereference knode_klist(n)->put on an already removed node, resulting in a NULL pointer dereference.
This race was introduced by commit 27aabf27fd01 ("Bluetooth: fix use-after-free in device_for_each_child()"), which replaced device_find_child(..., __match_tty) with device_find_any_child() in hci_conn_del_sysfs(). That change was intended to avoid a use-after-free where conn->dev outlived its parent hdev->dev when child devices held references to conn->dev, because conn->dev only held a reference to hdev->dev while registered in sysfs.
Fix the issue properly by taking an explicit reference to the parent device with get_device(&hdev->dev) in hci_conn_init_sysfs() and dropping it with put_device(parent) in bt_link_release() when the conn device is freed. This ensures that hdev->dev remains valid for the entire lifecycle of conn->dev, resolving the underlying use-after-free. With the parent reference held properly, restore the __match_tty filter in hci_conn_del_sysfs() so that device_move() is only invoked on persistent RFCOMM TTY devices as originally intended, eliminating the race condition with unregistering network devices.
{
"affected": [],
"aliases": [
"CVE-2026-97975"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:25Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: hci_sysfs: Fix NULL pointer dereference in device_del()\n\nA NULL pointer dereference in klist_put() occurs when a child device (such\nas a BNEP network device in bnep_session) is concurrently being\nunregistered while hci_conn_del_sysfs() reparents child devices.\n\nThis is caused by a race condition between hci_conn_del_sysfs() and\nconcurrent child device unregistration (e.g. bnep_session calling\nunregister_netdev()). During device unregistration, device_del() snapshots\na non-NULL parent pointer. Concurrently, hci_conn_del_sysfs() finds the\nchild device using device_find_any_child() and calls device_move() to\nreparent it to NULL, which removes the node from its parent\u0027s klist and\nclears knode_parent. Subsequently, device_del() calls\nklist_del(\u0026dev-\u003ep-\u003eknode_parent) using the stale parent snapshot, causing\nklist_put() to dereference knode_klist(n)-\u003eput on an already removed node,\nresulting in a NULL pointer dereference.\n\nThis race was introduced by commit 27aabf27fd01 (\"Bluetooth: fix\nuse-after-free in device_for_each_child()\"), which replaced\ndevice_find_child(..., __match_tty) with device_find_any_child() in\nhci_conn_del_sysfs(). That change was intended to avoid a use-after-free\nwhere conn-\u003edev outlived its parent hdev-\u003edev when child devices held\nreferences to conn-\u003edev, because conn-\u003edev only held a reference to\nhdev-\u003edev while registered in sysfs.\n\nFix the issue properly by taking an explicit reference to the parent device\nwith get_device(\u0026hdev-\u003edev) in hci_conn_init_sysfs() and dropping it with\nput_device(parent) in bt_link_release() when the conn device is freed. This\nensures that hdev-\u003edev remains valid for the entire lifecycle of conn-\u003edev,\nresolving the underlying use-after-free. With the parent reference held\nproperly, restore the __match_tty filter in hci_conn_del_sysfs() so that\ndevice_move() is only invoked on persistent RFCOMM TTY devices as\noriginally intended, eliminating the race condition with unregistering\nnetwork devices.",
"id": "GHSA-2vfm-8xc8-7w2c",
"modified": "2026-09-25T12:31:31Z",
"published": "2026-09-25T12:31:31Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97975"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9b851b09b392da68bd715601f10a5adb2d8d19b8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9e9ece97b8e716890793de261574b8efef7d8702"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/eeabdb25c3209569367e99a85ca9a503b64a646d"
}
],
"schema_version": "1.4.0",
"severity": []
}
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