[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>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index bfc9a35bad33..1dae3dfc66a9 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -665,7 +665,8 @@ 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;
@@ -674,7 +675,8 @@ 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);
         }