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authorGustavo F. Padovan <padovan@profusion.mobi>2010-09-21 16:31:11 -0300
committerGustavo F. Padovan <padovan@profusion.mobi>2010-09-30 12:19:35 -0300
commite454c844644683571617896ab2a4ce0109c1943e (patch)
treefd8fbcb76608bce78062c6a74ff8e8b65b3e34ae /include/net
parentb0239c80fe89d5832a68a0f3121a9d5ec9fb763e (diff)
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Bluetooth: Fix deadlock in the ERTM logic
The Enhanced Retransmission Mode(ERTM) is a realiable mode of operation of the Bluetooth L2CAP layer. Think on it like a simplified version of TCP. The problem we were facing here was a deadlock. ERTM uses a backlog queue to queue incomimg packets while the user is helding the lock. At some moment the sk_sndbuf can be exceeded and we can't alloc new skbs then the code sleep with the lock to wait for memory, that stalls the ERTM connection once we can't read the acknowledgements packets in the backlog queue to free memory and make the allocation of outcoming skb successful. This patch actually affect all users of bt_skb_send_alloc(), i.e., all L2CAP modes and SCO. We are safe against socket states changes or channels deletion while the we are sleeping wait memory. Checking for the sk->sk_err and sk->sk_shutdown make the code safe, since any action that can leave the socket or the channel in a not usable state set one of the struct members at least. Then we can check both of them when getting the lock again and return with the proper error if something unexpected happens. Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi> Signed-off-by: Ulisses Furquim <ulisses@profusion.mobi>
Diffstat (limited to 'include/net')
-rw-r--r--include/net/bluetooth/bluetooth.h18
1 files changed, 18 insertions, 0 deletions
diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index 27a902d9b3a..30fce0128dd 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -161,12 +161,30 @@ static inline struct sk_buff *bt_skb_send_alloc(struct sock *sk, unsigned long l
{
struct sk_buff *skb;
+ release_sock(sk);
if ((skb = sock_alloc_send_skb(sk, len + BT_SKB_RESERVE, nb, err))) {
skb_reserve(skb, BT_SKB_RESERVE);
bt_cb(skb)->incoming = 0;
}
+ lock_sock(sk);
+
+ if (!skb && *err)
+ return NULL;
+
+ *err = sock_error(sk);
+ if (*err)
+ goto out;
+
+ if (sk->sk_shutdown) {
+ *err = -ECONNRESET;
+ goto out;
+ }
return skb;
+
+out:
+ kfree_skb(skb);
+ return NULL;
}
int bt_err(__u16 code);