[PATCH v4 1/3] Bluetooth: bnep: fix possible might sleep error in bnep_session

Jeffy Chen
2017-02-14T00:56:16Z

It looks like bnep_session has same pattern as the issue reported in
old rfcomm:

while (1) {
set_current_state(TASK_INTERRUPTIBLE);
if (condition)
break;
// may call might_sleep here
schedule();
}
__set_current_state(TASK_RUNNING);

Which fixed at:
dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
---

Changes in v3:
Add brian's Reviewed-by.

Changes in v2:
Remove unnecessary memory barrier before wake_up_* functions.

net/bluetooth/bnep/core.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index fbf251f..4d6b94d 100644
--- a/net/bluetooth/bnep/core.c
+++ b/net/bluetooth/bnep/core.c
@@ -484,16 +484,16 @@ static int bnep_session(void *arg)
struct net_device *dev = s->dev;
struct sock *sk = s->sock->sk;
struct sk_buff *skb;
- wait_queue_t wait;
+ DEFINE_WAIT_FUNC(wait, woken_wake_function);

BT_DBG("");

set_user_nice(current, -15);

- init_waitqueue_entry(&wait, current);
add_wait_queue(sk_sleep(sk), &wait);
while (1) {
- set_current_state(TASK_INTERRUPTIBLE);
+ /* Ensure session->terminate is updated */
+ smp_mb__before_atomic();

if (atomic_read(&s->terminate))
break;
@@ -515,9 +515,8 @@ static int bnep_session(void *arg)
break;
netif_wake_queue(dev);

- schedule();
+ wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
- __set_current_state(TASK_RUNNING);
remove_wait_queue(sk_sleep(sk), &wait);

/* Cleanup session */
@@ -666,7 +665,7 @@ int bnep_del_connection(struct bnep_conndel_req *req)
s = __bnep_get_session(req->dst);
if (s) {
atomic_inc(&s->terminate);
- wake_up_process(s->task);
+ wake_up_interruptible(sk_sleep(s->sock->sk));
} else
err = -ENOENT;

--
2.1.4