[PATCH 1/2] Bluetooth: SCO: Fix possible circular locking dependency on sco_connect_cfm

oficerovas
2024-02-12T13:10:14Z

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

commit 9a8ec9e8ebb5 ("Bluetooth: SCO: Fix possible circular locking dependency on sco_connect_cfm")

This attempts to fix the following trace:

======================================================
WARNING: possible circular locking dependency detected
6.3.0-rc2-g0b93eeba4454 #4703 Not tainted
------------------------------------------------------
kworker/u3:0/46 is trying to acquire lock:
ffff888001fd9130 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at:
sco_connect_cfm+0x118/0x4a0

but task is already holding lock:
ffffffff831e3340 (hci_cb_list_lock){+.+.}-{3:3}, at:
hci_sync_conn_complete_evt+0x1ad/0x3d0

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+0x13b/0xcc0
hci_sync_conn_complete_evt+0x1ad/0x3d0
hci_event_packet+0x55c/0x7c0
hci_rx_work+0x34c/0xa00
process_one_work+0x575/0x910
worker_thread+0x89/0x6f0
kthread+0x14e/0x180
ret_from_fork+0x2b/0x50

-> #1 (&hdev->lock){+.+.}-{3:3}:
__mutex_lock+0x13b/0xcc0
sco_sock_connect+0xfc/0x630
__sys_connect+0x197/0x1b0
__x64_sys_connect+0x37/0x50
do_syscall_64+0x42/0x90
entry_SYSCALL_64_after_hwframe+0x70/0xda

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
__lock_acquire+0x18cc/0x3740
lock_acquire+0x151/0x3a0
lock_sock_nested+0x32/0x80
sco_connect_cfm+0x118/0x4a0
hci_sync_conn_complete_evt+0x1e6/0x3d0
hci_event_packet+0x55c/0x7c0
hci_rx_work+0x34c/0xa00
process_one_work+0x575/0x910
worker_thread+0x89/0x6f0
kthread+0x14e/0x180
ret_from_fork+0x2b/0x50

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 ***

4 locks held by kworker/u3:0/46:
#0: ffff8880028d1130 ((wq_completion)hci0#2){+.+.}-{0:0}, at:
process_one_work+0x4c0/0x910
#1: ffff8880013dfde0 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0},
at: process_one_work+0x4c0/0x910
#2: ffff8880025d8070 (&hdev->lock){+.+.}-{3:3}, at:
hci_sync_conn_complete_evt+0xa6/0x3d0
#3: ffffffffb79e3340 (hci_cb_list_lock){+.+.}-{3:3}, at:
hci_sync_conn_complete_evt+0x1ad/0x3d0

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Alexander Ofitserov <oficerovas@altlinux.org>
---
net/bluetooth/sco.c | 69 ++++++++++++++++++++++++++-------------------
1 file changed, 40 insertions(+), 29 deletions(-)

diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 6d4168cfeb563..0e1f5dde7bfec 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -235,27 +235,41 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk,
return err;
}

-static int sco_connect(struct hci_dev *hdev, struct sock *sk)
+static int sco_connect(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)))
- return -EOPNOTSUPP;
+ (!lmp_transp_capable(hdev) || !lmp_esco_capable(hdev))) {
+ err = -EOPNOTSUPP;
+ goto unlock;
+ }

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

conn = sco_conn_add(hcon);
if (!conn) {
@@ -263,13 +277,15 @@ static int sco_connect(struct hci_dev *hdev, struct sock *sk)
return -ENOMEM;
}

- /* Update source addr of the socket */
- bacpy(&sco_pi(sk)->src, &hcon->src);
-
err = sco_chan_add(conn, sk, NULL);
if (err)
return err;

+ lock_sock(sk);
+
+ /* Update source addr of the socket */
+ bacpy(&sco_pi(sk)->src, &hcon->src);
+
if (hcon->state == BT_CONNECTED) {
sco_sock_clear_timer(sk);
sk->sk_state = BT_CONNECTED;
@@ -278,6 +294,13 @@ static int sco_connect(struct hci_dev *hdev, struct sock *sk)
sco_sock_set_timer(sk, sk->sk_sndtimeo);
}

+ release_sock(sk);
+
+ return err;
+
+unlock:
+ hci_dev_unlock(hdev);
+ hci_dev_put(hdev);
return err;
}

@@ -565,7 +588,6 @@ 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);
@@ -574,37 +596,26 @@ static int sco_sock_connect(struct socket *sock, struct sockaddr *addr, int alen
addr->sa_family != AF_BLUETOOTH)
return -EINVAL;

- lock_sock(sk);
- if (sk->sk_state != BT_OPEN && sk->sk_state != BT_BOUND) {
- err = -EBADFD;
- goto done;
- }
+ if (sk->sk_state != BT_OPEN && sk->sk_state != BT_BOUND)
+ return -EBADFD;

- if (sk->sk_type != SOCK_SEQPACKET) {
+ if (sk->sk_type != SOCK_SEQPACKET)
err = -EINVAL;
- goto done;
- }
-
- hdev = hci_get_route(&sa->sco_bdaddr, &sco_pi(sk)->src, BDADDR_BREDR);
- if (!hdev) {
- err = -EHOSTUNREACH;
- goto done;
- }
- hci_dev_lock(hdev);

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

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

err = bt_sock_wait_state(sk, BT_CONNECTED,
sock_sndtimeo(sk, flags & O_NONBLOCK));

-done:
release_sock(sk);
return err;
}
--
2.42.1