[PATCH] BLUETOOTH: Fix locking in hci_sock_dev_event().

We presently use lock_sock() to acquire a lock on a socket in
hci_sock_dev_event(), but this goes BUG because lock_sock()
can sleep and we're already holding a read-write spinlock at
that point. So, we must use the non-sleeping BH version,
bh_lock_sock().

However, hci_sock_dev_event() is called from user context and
hence using simply bh_lock_sock() will deadlock against a
concurrent softirq that tries to acquire a lock on the same
socket. Hence, disabling BH's before acquiring the socket lock
and enable them afterwards, is the proper solution to fix
socket locking in hci_sock_dev_event().

Signed-off-by: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index 71f5cfbbebb834ce1ffa3283cde1f00db372b580..2f6e1ea6a5cc1a71c61c0ad666ab92f7821d504a 100644 (file)
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -656,7 +656,8 @@ static int hci_sock_dev_event(struct notifier_block *this, unsigned long event,
                /* Detach sockets from device */
                read_lock(&hci_sk_list.lock);
                sk_for_each(sk, node, &hci_sk_list.head) {
-                       lock_sock(sk);
+                       local_bh_disable();
+                       bh_lock_sock_nested(sk);
                        if (hci_pi(sk)->hdev == hdev) {
                                hci_pi(sk)->hdev = NULL;
                                sk->sk_err = EPIPE;
@@ -665,7 +666,8 @@ static int hci_sock_dev_event(struct notifier_block *this, unsigned long event,
 
                                hci_dev_put(hdev);
                        }
-                       release_sock(sk);
+                       bh_unlock_sock(sk);
+                       local_bh_enable();
                }
                read_unlock(&hci_sk_list.lock);
        }