[patch 54/54] BLUETOOTH: Fix locking in hci_sock_dev_event().

Chris Wright
2007-06-08T08:00:50Z

[-- Attachment #1: bluetooth-fix-locking-in-hci_sock_dev_event.patch --]
[-- Type: text/plain, Size: 1784 bytes --]

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

From: Satyam Sharma <ssatyam@cse.iitk.ac.in>

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

--- linux-2.6.21.4.orig/net/bluetooth/hci_sock.c
+++ linux-2.6.21.4/net/bluetooth/hci_sock.c
@@ -656,7 +656,8 @@ 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;
@@ -665,7 +666,8 @@ 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);
}

--