[PATCH 4.20 73/76] Bluetooth: Fix locking in bt_accept_enqueue() for BH context

Greg Kroah-Hartman
2019-03-08T12:57:09Z

From: Matthias Kaehlcke <mka@chromium.org>

commit c4f5627f7eeecde1bb6b646d8c0907b96dc2b2a6 upstream.

With commit e16337622016 ("Bluetooth: Handle bt_accept_enqueue() socket
atomically") lock_sock[_nested]() is used to acquire the socket lock
before manipulating the socket. lock_sock[_nested]() may block, which
is problematic since bt_accept_enqueue() can be called in bottom half
context (e.g. from rfcomm_connect_ind()):

[<ffffff80080d81ec>] __might_sleep+0x4c/0x80
[<ffffff800876c7b0>] lock_sock_nested+0x24/0x58
[<ffffff8000d7c27c>] bt_accept_enqueue+0x48/0xd4 [bluetooth]
[<ffffff8000e67d8c>] rfcomm_connect_ind+0x190/0x218 [rfcomm]

Add a parameter to bt_accept_enqueue() to indicate whether the
function is called from BH context, and acquire the socket lock
with bh_lock_sock_nested() if that's the case.

Also adapt all callers of bt_accept_enqueue() to pass the new
parameter:

- l2cap_sock_new_connection_cb()
- uses lock_sock() to lock the parent socket => process context

- rfcomm_connect_ind()
- acquires the parent socket lock with bh_lock_sock() => BH
context

- __sco_chan_add()
- called from sco_chan_add(), which is called from sco_connect().
parent is NULL, hence bt_accept_enqueue() isn't called in this
code path and we can ignore it
- also called from sco_conn_ready(). uses bh_lock_sock() to acquire
the parent lock => BH context

Fixes: e16337622016 ("Bluetooth: Handle bt_accept_enqueue() socket atomically")
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/net/bluetooth/bluetooth.h | 2 +-
net/bluetooth/af_bluetooth.c | 16 +++++++++++++---
net/bluetooth/l2cap_sock.c | 2 +-
net/bluetooth/rfcomm/sock.c | 2 +-
net/bluetooth/sco.c | 2 +-
5 files changed, 17 insertions(+), 7 deletions(-)

--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -276,7 +276,7 @@ int bt_sock_ioctl(struct socket *sock,
int bt_sock_wait_state(struct sock *sk, int state, unsigned long timeo);
int bt_sock_wait_ready(struct sock *sk, unsigned long flags);

-void bt_accept_enqueue(struct sock *parent, struct sock *sk);
+void bt_accept_enqueue(struct sock *parent, struct sock *sk, bool bh);
void bt_accept_unlink(struct sock *sk);
struct sock *bt_accept_dequeue(struct sock *parent, struct socket *newsock);

--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -154,15 +154,25 @@ void bt_sock_unlink(struct bt_sock_list
}
EXPORT_SYMBOL(bt_sock_unlink);

-void bt_accept_enqueue(struct sock *parent, struct sock *sk)
+void bt_accept_enqueue(struct sock *parent, struct sock *sk, bool bh)
{
BT_DBG("parent %p, sk %p", parent, sk);

sock_hold(sk);
- lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
+
+ if (bh)
+ bh_lock_sock_nested(sk);
+ else
+ lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
+
list_add_tail(&bt_sk(sk)->accept_q, &bt_sk(parent)->accept_q);
bt_sk(sk)->parent = parent;
- release_sock(sk);
+
+ if (bh)
+ bh_unlock_sock(sk);
+ else
+ release_sock(sk);
+
parent->sk_ack_backlog++;
}
EXPORT_SYMBOL(bt_accept_enqueue);
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1252,7 +1252,7 @@ static struct l2cap_chan *l2cap_sock_new

l2cap_sock_init(sk, parent);

- bt_accept_enqueue(parent, sk);
+ bt_accept_enqueue(parent, sk, false);

release_sock(parent);

--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -988,7 +988,7 @@ int rfcomm_connect_ind(struct rfcomm_ses
rfcomm_pi(sk)->channel = channel;

sk->sk_state = BT_CONFIG;
- bt_accept_enqueue(parent, sk);
+ bt_accept_enqueue(parent, sk, true);

/* Accept connection and return socket DLC */
*d = rfcomm_pi(sk)->dlc;
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -193,7 +193,7 @@ static void __sco_chan_add(struct sco_co
conn->sk = sk;

if (parent)
- bt_accept_enqueue(parent, sk);
+ bt_accept_enqueue(parent, sk, true);
}

static int sco_chan_add(struct sco_conn *conn, struct sock *sk,