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Bluetooth: defer cleanup of resources in hci_unregister_dev()

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syzbot is hitting might_sleep() warning at hci_sock_dev_event() due to
calling lock_sock() with rw spinlock held [1].

It seems that history of this locking problem is a trial and error.

Commit b40df5743e ("[PATCH] bluetooth: fix socket locking in
hci_sock_dev_event()") in 2.6.21-rc4 changed bh_lock_sock() to
lock_sock() as an attempt to fix lockdep warning.

Then, commit 4ce61d1c7a ("[BLUETOOTH]: Fix locking in
hci_sock_dev_event().") in 2.6.22-rc2 changed lock_sock() to
local_bh_disable() + bh_lock_sock_nested() as an attempt to fix the
sleep in atomic context warning.

Then, commit 4b5dd696f8 ("Bluetooth: Remove local_bh_disable() from
hci_sock.c") in 3.3-rc1 removed local_bh_disable().

Then, commit e305509e67 ("Bluetooth: use correct lock to prevent UAF
of hdev object") in 5.13-rc5 again changed bh_lock_sock_nested() to
lock_sock() as an attempt to fix CVE-2021-3573.

This difficulty comes from current implementation that
hci_sock_dev_event(HCI_DEV_UNREG) is responsible for dropping all
references from sockets because hci_unregister_dev() immediately
reclaims resources as soon as returning from
hci_sock_dev_event(HCI_DEV_UNREG).

But the history suggests that hci_sock_dev_event(HCI_DEV_UNREG) was not
doing what it should do.

Therefore, instead of trying to detach sockets from device, let's accept
not detaching sockets from device at hci_sock_dev_event(HCI_DEV_UNREG),
by moving actual cleanup of resources from hci_unregister_dev() to
hci_cleanup_dev() which is called by bt_host_release() when all
references to this unregistered device (which is a kobject) are gone.

Since hci_sock_dev_event(HCI_DEV_UNREG) no longer resets
hci_pi(sk)->hdev, we need to check whether this device was unregistered
and return an error based on HCI_UNREGISTER flag.  There might be subtle
behavioral difference in "monitor the hdev" functionality; please report
if you found something went wrong due to this patch.

Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9 [1]
Reported-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: e305509e67 ("Bluetooth: use correct lock to prevent UAF of hdev object")
Acked-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Tetsuo Handa 2021-08-04 19:26:56 +09:00 committed by Linus Torvalds
parent 0b53abfc5f
commit e04480920d
4 changed files with 45 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/net/bluetooth/hci_core.h
View File

@ -1230,6 +1230,7 @@ struct hci_dev *hci_alloc_dev(void);
void hci_free_dev(struct hci_dev *hdev);
int hci_register_dev(struct hci_dev *hdev);
void hci_unregister_dev(struct hci_dev *hdev);
void hci_cleanup_dev(struct hci_dev *hdev);
int hci_suspend_dev(struct hci_dev *hdev);
int hci_resume_dev(struct hci_dev *hdev);
int hci_reset_dev(struct hci_dev *hdev);

16
net/bluetooth/hci_core.c
View File

@ -3996,14 +3996,10 @@ EXPORT_SYMBOL(hci_register_dev);
/* Unregister HCI device */
void hci_unregister_dev(struct hci_dev *hdev)
{
int id;
BT_DBG("%p name %s bus %d", hdev, hdev->name, hdev->bus);
hci_dev_set_flag(hdev, HCI_UNREGISTER);
id = hdev->id;
write_lock(&hci_dev_list_lock);
list_del(&hdev->list);
write_unlock(&hci_dev_list_lock);
@ -4038,7 +4034,14 @@ void hci_unregister_dev(struct hci_dev *hdev)
}
device_del(&hdev->dev);
/* Actual cleanup is deferred until hci_cleanup_dev(). */
hci_dev_put(hdev);
}
EXPORT_SYMBOL(hci_unregister_dev);
/* Cleanup HCI device */
void hci_cleanup_dev(struct hci_dev *hdev)
{
debugfs_remove_recursive(hdev->debugfs);
kfree_const(hdev->hw_info);
kfree_const(hdev->fw_info);
@ -4063,11 +4066,8 @@ void hci_unregister_dev(struct hci_dev *hdev)
hci_blocked_keys_clear(hdev);
hci_dev_unlock(hdev);
hci_dev_put(hdev);
ida_simple_remove(&hci_index_ida, id);
ida_simple_remove(&hci_index_ida, hdev->id);
}
EXPORT_SYMBOL(hci_unregister_dev);
/* Suspend HCI device */
int hci_suspend_dev(struct hci_dev *hdev)

49
net/bluetooth/hci_sock.c
View File

@ -59,6 +59,17 @@ struct hci_pinfo {
char comm[TASK_COMM_LEN];
};
static struct hci_dev *hci_hdev_from_sock(struct sock *sk)
{
struct hci_dev *hdev = hci_pi(sk)->hdev;
if (!hdev)
return ERR_PTR(-EBADFD);
if (hci_dev_test_flag(hdev, HCI_UNREGISTER))
return ERR_PTR(-EPIPE);
return hdev;
}
void hci_sock_set_flag(struct sock *sk, int nr)
{
set_bit(nr, &hci_pi(sk)->flags);
@ -759,19 +770,13 @@ void hci_sock_dev_event(struct hci_dev *hdev, int event)
if (event == HCI_DEV_UNREG) {
struct sock *sk;
/* Detach sockets from device */
/* Wake up sockets using this dead device */
read_lock(&hci_sk_list.lock);
sk_for_each(sk, &hci_sk_list.head) {
lock_sock(sk);
if (hci_pi(sk)->hdev == hdev) {
hci_pi(sk)->hdev = NULL;
sk->sk_err = EPIPE;
sk->sk_state = BT_OPEN;
sk->sk_state_change(sk);
hci_dev_put(hdev);
}
release_sock(sk);
}
read_unlock(&hci_sk_list.lock);
}
@ -930,10 +935,10 @@ static int hci_sock_reject_list_del(struct hci_dev *hdev, void __user *arg)
static int hci_sock_bound_ioctl(struct sock *sk, unsigned int cmd,
unsigned long arg)
{
struct hci_dev *hdev = hci_pi(sk)->hdev;
struct hci_dev *hdev = hci_hdev_from_sock(sk);
if (!hdev)
return -EBADFD;
if (IS_ERR(hdev))
return PTR_ERR(hdev);
if (hci_dev_test_flag(hdev, HCI_USER_CHANNEL))
return -EBUSY;
@ -1103,6 +1108,18 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr,
lock_sock(sk);
/* Allow detaching from dead device and attaching to alive device, if
* the caller wants to re-bind (instead of close) this socket in
* response to hci_sock_dev_event(HCI_DEV_UNREG) notification.
*/
hdev = hci_pi(sk)->hdev;
if (hdev && hci_dev_test_flag(hdev, HCI_UNREGISTER)) {
hci_pi(sk)->hdev = NULL;
sk->sk_state = BT_OPEN;
hci_dev_put(hdev);
}
hdev = NULL;
if (sk->sk_state == BT_BOUND) {
err = -EALREADY;
goto done;
@ -1379,9 +1396,9 @@ static int hci_sock_getname(struct socket *sock, struct sockaddr *addr,
lock_sock(sk);
hdev = hci_pi(sk)->hdev;
if (!hdev) {
err = -EBADFD;
hdev = hci_hdev_from_sock(sk);
if (IS_ERR(hdev)) {
err = PTR_ERR(hdev);
goto done;
}
@ -1743,9 +1760,9 @@ static int hci_sock_sendmsg(struct socket *sock, struct msghdr *msg,
goto done;
}
hdev = hci_pi(sk)->hdev;
if (!hdev) {
err = -EBADFD;
hdev = hci_hdev_from_sock(sk);
if (IS_ERR(hdev)) {
err = PTR_ERR(hdev);
goto done;
}

3
net/bluetooth/hci_sysfs.c
View File

@ -83,6 +83,9 @@ void hci_conn_del_sysfs(struct hci_conn *conn)
static void bt_host_release(struct device *dev)
{
struct hci_dev *hdev = to_hci_dev(dev);
if (hci_dev_test_flag(hdev, HCI_UNREGISTER))
hci_cleanup_dev(hdev);
kfree(hdev);
module_put(THIS_MODULE);
}