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Commit 4ce61d1c authored by Satyam Sharma's avatar Satyam Sharma Committed by David S. Miller
Browse files

[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: default avatarSatyam Sharma <ssatyam@cse.iitk.ac.in>
Signed-off-by: default avatarMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 689d7946

net/bluetooth/hci_sock.c

+4 −2
Original line number Diff line number Diff line
@@ -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);

	}