[PATCH] bluetooth: fix locking in hci_sock_dev_event()

[Satyam Sharma <ssatyam@cse.iitk.ac.in>]

[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().

Cc: David Miller <davem@davemloft.net>
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>

---

 net/bluetooth/hci_sock.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

---

diff -ruNp a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
--- a/net/bluetooth/hci_sock.c	2007-05-16 17:31:06.000000000 +0530
+++ b/net/bluetooth/hci_sock.c	2007-05-16 17:38:35.000000000 +0530
@@ -665,7 +665,8 @@ static int hci_sock_dev_event(struct not
 		/* 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 not

 				hci_dev_put(hdev);
 			}
-			release_sock(sk);
+			bh_unlock_sock(sk);
+			local_bh_enable();
 		}
 		read_unlock(&hci_sk_list.lock);
 	}

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/