[PATCH AUTOSEL 4.9 31/48] Bluetooth: avoid circular locks in sco_sock_connect

Sasha Levin
2021-09-09T13:26:11Z

From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>

[ Upstream commit 734bc5ff783115aa3164f4e9dd5967ae78e0a8ab ]

In a future patch, calls to bh_lock_sock in sco.c should be replaced
by lock_sock now that none of the functions are run in IRQ context.

However, doing so results in a circular locking dependency:

======================================================
WARNING: possible circular locking dependency detected
5.14.0-rc4-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/14867 is trying to acquire lock:
ffff88803e3c1120 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at:
lock_sock include/net/sock.h:1613 [inline]
ffff88803e3c1120 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at:
sco_conn_del+0x12a/0x2a0 net/bluetooth/sco.c:191

but task is already holding lock:
ffffffff8d2dc7c8 (hci_cb_list_lock){+.+.}-{3:3}, at:
hci_disconn_cfm include/net/bluetooth/hci_core.h:1497 [inline]
ffffffff8d2dc7c8 (hci_cb_list_lock){+.+.}-{3:3}, at:
hci_conn_hash_flush+0xda/0x260 net/bluetooth/hci_conn.c:1608

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (hci_cb_list_lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:959 [inline]
__mutex_lock+0x12a/0x10a0 kernel/locking/mutex.c:1104
hci_connect_cfm include/net/bluetooth/hci_core.h:1482 [inline]
hci_remote_features_evt net/bluetooth/hci_event.c:3263 [inline]
hci_event_packet+0x2f4d/0x7c50 net/bluetooth/hci_event.c:6240
hci_rx_work+0x4f8/0xd30 net/bluetooth/hci_core.c:5122
process_one_work+0x98d/0x1630 kernel/workqueue.c:2276
worker_thread+0x658/0x11f0 kernel/workqueue.c:2422
kthread+0x3e5/0x4d0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

-> #1 (&hdev->lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:959 [inline]
__mutex_lock+0x12a/0x10a0 kernel/locking/mutex.c:1104
sco_connect net/bluetooth/sco.c:245 [inline]
sco_sock_connect+0x227/0xa10 net/bluetooth/sco.c:601
__sys_connect_file+0x155/0x1a0 net/socket.c:1879
__sys_connect+0x161/0x190 net/socket.c:1896
__do_sys_connect net/socket.c:1906 [inline]
__se_sys_connect net/socket.c:1903 [inline]
__x64_sys_connect+0x6f/0xb0 net/socket.c:1903
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3051 [inline]
check_prevs_add kernel/locking/lockdep.c:3174 [inline]
validate_chain kernel/locking/lockdep.c:3789 [inline]
__lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
lock_acquire kernel/locking/lockdep.c:5625 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
lock_sock_nested+0xca/0x120 net/core/sock.c:3170
lock_sock include/net/sock.h:1613 [inline]
sco_conn_del+0x12a/0x2a0 net/bluetooth/sco.c:191
sco_disconn_cfm+0x71/0xb0 net/bluetooth/sco.c:1202
hci_disconn_cfm include/net/bluetooth/hci_core.h:1500 [inline]
hci_conn_hash_flush+0x127/0x260 net/bluetooth/hci_conn.c:1608
hci_dev_do_close+0x528/0x1130 net/bluetooth/hci_core.c:1778
hci_unregister_dev+0x1c0/0x5a0 net/bluetooth/hci_core.c:4015
vhci_release+0x70/0xe0 drivers/bluetooth/hci_vhci.c:340
__fput+0x288/0x920 fs/file_table.c:280
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0xbd4/0x2a60 kernel/exit.c:825
do_group_exit+0x125/0x310 kernel/exit.c:922
get_signal+0x47f/0x2160 kernel/signal.c:2808
arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:865
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
ret_from_fork+0x15/0x30 arch/x86/entry/entry_64.S:288

other info that might help us debug this:

Chain exists of:
sk_lock-AF_BLUETOOTH-BTPROTO_SCO --> &hdev->lock --> hci_cb_list_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(hci_cb_list_lock);
lock(&hdev->lock);
lock(hci_cb_list_lock);
lock(sk_lock-AF_BLUETOOTH-BTPROTO_SCO);

*** DEADLOCK ***

The issue is that the lock hierarchy should go from &hdev->lock -->
hci_cb_list_lock --> sk_lock-AF_BLUETOOTH-BTPROTO_SCO. For example,
one such call trace is:

hci_dev_do_close():
hci_dev_lock();
hci_conn_hash_flush():
hci_disconn_cfm():
mutex_lock(&hci_cb_list_lock);
sco_disconn_cfm():
sco_conn_del():
lock_sock(sk);

However, in sco_sock_connect, we call lock_sock before calling
hci_dev_lock inside sco_connect, thus inverting the lock hierarchy.

We fix this by pulling the call to hci_dev_lock out from sco_connect.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/bluetooth/sco.c | 39 ++++++++++++++++-----------------------
1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 95fd7a837dc5..5993a3843c61 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -210,44 +210,32 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk,
return err;
}

-static int sco_connect(struct sock *sk)
+static int sco_connect(struct hci_dev *hdev, struct sock *sk)
{
struct sco_conn *conn;
struct hci_conn *hcon;
- struct hci_dev *hdev;
int err, type;

BT_DBG("%pMR -> %pMR", &sco_pi(sk)->src, &sco_pi(sk)->dst);

- hdev = hci_get_route(&sco_pi(sk)->dst, &sco_pi(sk)->src, BDADDR_BREDR);
- if (!hdev)
- return -EHOSTUNREACH;
-
- hci_dev_lock(hdev);
-
if (lmp_esco_capable(hdev) && !disable_esco)
type = ESCO_LINK;
else
type = SCO_LINK;

if (sco_pi(sk)->setting == BT_VOICE_TRANSPARENT &&
- (!lmp_transp_capable(hdev) || !lmp_esco_capable(hdev))) {
- err = -EOPNOTSUPP;
- goto done;
- }
+ (!lmp_transp_capable(hdev) || !lmp_esco_capable(hdev)))
+ return -EOPNOTSUPP;

hcon = hci_connect_sco(hdev, type, &sco_pi(sk)->dst,
sco_pi(sk)->setting);
- if (IS_ERR(hcon)) {
- err = PTR_ERR(hcon);
- goto done;
- }
+ if (IS_ERR(hcon))
+ return PTR_ERR(hcon);

conn = sco_conn_add(hcon);
if (!conn) {
hci_conn_drop(hcon);
- err = -ENOMEM;
- goto done;
+ return -ENOMEM;
}

/* Update source addr of the socket */
@@ -255,7 +243,7 @@ static int sco_connect(struct sock *sk)

err = sco_chan_add(conn, sk, NULL);
if (err)
- goto done;
+ return err;

if (hcon->state == BT_CONNECTED) {
sco_sock_clear_timer(sk);
@@ -265,9 +253,6 @@ static int sco_connect(struct sock *sk)
sco_sock_set_timer(sk, sk->sk_sndtimeo);
}

-done:
- hci_dev_unlock(hdev);
- hci_dev_put(hdev);
return err;
}

@@ -555,6 +540,7 @@ static int sco_sock_connect(struct socket *sock, struct sockaddr *addr, int alen
{
struct sockaddr_sco *sa = (struct sockaddr_sco *) addr;
struct sock *sk = sock->sk;
+ struct hci_dev *hdev;
int err;

BT_DBG("sk %p", sk);
@@ -569,12 +555,19 @@ static int sco_sock_connect(struct socket *sock, struct sockaddr *addr, int alen
if (sk->sk_type != SOCK_SEQPACKET)
return -EINVAL;

+ hdev = hci_get_route(&sa->sco_bdaddr, &sco_pi(sk)->src, BDADDR_BREDR);
+ if (!hdev)
+ return -EHOSTUNREACH;
+ hci_dev_lock(hdev);
+
lock_sock(sk);

/* Set destination address and psm */
bacpy(&sco_pi(sk)->dst, &sa->sco_bdaddr);

- err = sco_connect(sk);
+ err = sco_connect(hdev, sk);
+ hci_dev_unlock(hdev);
+ hci_dev_put(hdev);
if (err)
goto done;

--
2.30.2