From 0e77f979a97d3d517fad0b51249ba6fb8ae2d365 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Wed, 4 Aug 2021 19:26:56 +0900 Subject: [PATCH] Bluetooth: defer cleanup of resources in hci_unregister_dev() [ Upstream commit e04480920d1eec9c061841399aa6f35b6f987d8b ] 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 b40df5743ee8 ("[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 4ce61d1c7a8e ("[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 4b5dd696f81b ("Bluetooth: Remove local_bh_disable() from hci_sock.c") in 3.3-rc1 removed local_bh_disable(). Then, commit e305509e678b ("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 Suggested-by: Linus Torvalds Signed-off-by: Tetsuo Handa Fixes: e305509e678b ("Bluetooth: use correct lock to prevent UAF of hdev object") Acked-by: Luiz Augusto von Dentz Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- include/net/bluetooth/hci_core.h | 1 + net/bluetooth/hci_core.c | 16 +++++------ net/bluetooth/hci_sock.c | 49 +++++++++++++++++++++----------- net/bluetooth/hci_sysfs.c | 3 ++ 4 files changed, 45 insertions(+), 24 deletions(-) diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h index 33db6c6d3fba..819796fb9d46 100644 --- a/include/net/bluetooth/hci_core.h +++ b/include/net/bluetooth/hci_core.h @@ -1028,6 +1028,7 @@ 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); diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c index 839c534bdcdb..8517da7f282e 100644 --- a/net/bluetooth/hci_core.c +++ b/net/bluetooth/hci_core.c @@ -3146,14 +3146,10 @@ 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); @@ -3182,7 +3178,14 @@ 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); @@ -3204,11 +3207,8 @@ void hci_unregister_dev(struct hci_dev *hdev) hci_discovery_filter_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) diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c index 35f5585188de..d30163eb1643 100644 --- a/net/bluetooth/hci_sock.c +++ b/net/bluetooth/hci_sock.c @@ -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); @@ -747,19 +758,13 @@ 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); } @@ -918,10 +923,10 @@ static int hci_sock_blacklist_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; @@ -1075,6 +1080,18 @@ 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; @@ -1351,9 +1368,9 @@ 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; } @@ -1713,9 +1730,9 @@ 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; } diff --git a/net/bluetooth/hci_sysfs.c b/net/bluetooth/hci_sysfs.c index ca7a35ebaefb..cb7d06bb0243 100644 --- a/net/bluetooth/hci_sysfs.c +++ b/net/bluetooth/hci_sysfs.c @@ -82,6 +82,9 @@ 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); } -- 2.20.1