github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-11 20:13:02 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

Bluetooth: hci_sysfs: Fix NULL pointer dereference in device_del()

Browse Source 
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 27aabf27fd ("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.

Fixes: 27aabf27fd ("Bluetooth: fix use-after-free in device_for_each_child()")
Assisted-by: Gemini:gemini-3.7-flash syzbot
Reported-by: syzbot+6df45dd3d03e1a9aca96@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=6df45dd3d03e1a9aca96
Link: https://syzkaller.appspot.com/ai_job?id=f1c0e740-db21-40af-a9ff-84db0fd8b8bd
Signed-off-by: Krystian Kaniewski <krystianmkaniewski@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
This commit is contained in:
Krystian Kaniewski 2026-09-04 12:24:22 +00:00 committed by Luiz Augusto von Dentz
parent 3d8a8e81ea
commit 9b851b09b3
1 changed files with 15 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
net/bluetooth/hci_sysfs.c
View File

@ -13,7 +13,10 @@ static const struct class bt_class = {
static void bt_link_release(struct device *dev)
{
struct hci_conn *conn = to_hci_conn(dev);
struct device *parent = dev->parent;
kfree(conn);
put_device(parent);
}
static const struct device_type bt_link = {
@ -21,6 +24,16 @@ static const struct device_type bt_link = {
.release = bt_link_release,
};
/*
* The rfcomm tty device will possibly retain even when conn
* is down, and sysfs doesn't support move zombie device,
* so we should move the device before conn device is destroyed.
*/
static int __match_tty(struct device *dev, const void *data)
{
return !strncmp(dev_name(dev), "rfcomm", 6);
}
void hci_conn_init_sysfs(struct hci_conn *conn)
{
struct hci_dev *hdev = conn->hdev;
@ -29,7 +42,7 @@ void hci_conn_init_sysfs(struct hci_conn *conn)
conn->dev.type = &bt_link;
conn->dev.class = &bt_class;
conn->dev.parent = &hdev->dev;
conn->dev.parent = get_device(&hdev->dev);
device_initialize(&conn->dev);
}
@ -69,7 +82,7 @@ void hci_conn_del_sysfs(struct hci_conn *conn)
while (1) {
struct device *dev;
dev = device_find_any_child(&conn->dev);
dev = device_find_child(&conn->dev, NULL, __match_tty);
if (!dev)
break;
device_move(dev, NULL, DPM_ORDER_DEV_LAST);