[PATCH 4.19 65/68] Bluetooth: Fix locking in bt_accept_enqueue() for BH context

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthias Kaehlcke <m...@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 <m...@chromium.org>
Reviewed-by: Douglas Anderson <diand...@chromium.org>
Signed-off-by: Marcel Holtmann <mar...@holtmann.org>
Cc: sta...@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gre...@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,