Bluetooth: Fix race condition on l2cap_ertm_send()
l2cap_ertm_send() can be called both from user context and bottom half
context. The socket locks for that contexts are different, the user
context uses a mutex(which can sleep) and the second one uses a
spinlock_bh. That creates a race condition when we have interruptions on
both contexts at the same time.
The better way to solve this is to add a new spinlock to lock
l2cap_ertm_send() and the vars it access. The other solution was to defer
l2cap_ertm_send() with a workqueue, but we the sending process already
has one defer on the hci layer. It's not a good idea add another one.
The patch refactor the code to create l2cap_retransmit_frames(), then we
encapulate the lock of l2cap_ertm_send() for some call. It also changes
l2cap_retransmit_frame() to l2cap_retransmit_one_frame() to avoid
confusion
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index d0185cc..7c695bf 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -353,6 +353,7 @@
__le16 sport;
+ spinlock_t send_lock;
struct timer_list retrans_timer;
struct timer_list monitor_timer;
struct timer_list ack_timer;
diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 9d514f9..fe663e9 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -1368,7 +1368,7 @@
return 0;
}
-static void l2cap_retransmit_frame(struct sock *sk, u8 tx_seq)
+static void l2cap_retransmit_one_frame(struct sock *sk, u8 tx_seq)
{
struct l2cap_pinfo *pi = l2cap_pi(sk);
struct sk_buff *skb, *tx_skb;
@@ -1467,10 +1467,29 @@
return nsent;
}
+static int l2cap_retransmit_frames(struct sock *sk)
+{
+ struct l2cap_pinfo *pi = l2cap_pi(sk);
+ int ret;
+
+ spin_lock_bh(&pi->send_lock);
+
+ if (!skb_queue_empty(TX_QUEUE(sk)))
+ sk->sk_send_head = TX_QUEUE(sk)->next;
+
+ pi->next_tx_seq = pi->expected_ack_seq;
+ ret = l2cap_ertm_send(sk);
+
+ spin_unlock_bh(&pi->send_lock);
+
+ return ret;
+}
+
static void l2cap_send_ack(struct l2cap_pinfo *pi)
{
struct sock *sk = (struct sock *)pi;
u16 control = 0;
+ int nframes;
control |= pi->buffer_seq << L2CAP_CTRL_REQSEQ_SHIFT;
@@ -1479,10 +1498,17 @@
pi->conn_state |= L2CAP_CONN_RNR_SENT;
l2cap_send_sframe(pi, control);
return;
- } else if (l2cap_ertm_send(sk) == 0) {
- control |= L2CAP_SUPER_RCV_READY;
- l2cap_send_sframe(pi, control);
}
+
+ spin_lock_bh(&pi->send_lock);
+ nframes = l2cap_ertm_send(sk);
+ spin_unlock_bh(&pi->send_lock);
+
+ if (nframes > 0)
+ return;
+
+ control |= L2CAP_SUPER_RCV_READY;
+ l2cap_send_sframe(pi, control);
}
static void l2cap_send_srejtail(struct sock *sk)
@@ -1673,8 +1699,10 @@
size += buflen;
}
skb_queue_splice_tail(&sar_queue, TX_QUEUE(sk));
+ spin_lock_bh(&pi->send_lock);
if (sk->sk_send_head == NULL)
sk->sk_send_head = sar_queue.next;
+ spin_unlock_bh(&pi->send_lock);
return size;
}
@@ -1745,8 +1773,15 @@
goto done;
}
__skb_queue_tail(TX_QUEUE(sk), skb);
+
+ if (pi->mode == L2CAP_MODE_ERTM)
+ spin_lock_bh(&pi->send_lock);
+
if (sk->sk_send_head == NULL)
sk->sk_send_head = skb;
+
+ if (pi->mode == L2CAP_MODE_ERTM)
+ spin_unlock_bh(&pi->send_lock);
} else {
/* Segment SDU into multiples PDUs */
err = l2cap_sar_segment_sdu(sk, msg, len);
@@ -1754,10 +1789,13 @@
goto done;
}
- if (pi->mode == L2CAP_MODE_STREAMING)
+ if (pi->mode == L2CAP_MODE_STREAMING) {
err = l2cap_streaming_send(sk);
- else
+ } else {
+ spin_lock_bh(&pi->send_lock);
err = l2cap_ertm_send(sk);
+ spin_unlock_bh(&pi->send_lock);
+ }
if (err >= 0)
err = len;
@@ -2321,6 +2359,7 @@
__skb_queue_head_init(SREJ_QUEUE(sk));
__skb_queue_head_init(BUSY_QUEUE(sk));
+ spin_lock_init(&l2cap_pi(sk)->send_lock);
INIT_WORK(&l2cap_pi(sk)->busy_work, l2cap_busy_work);
}
@@ -3340,7 +3379,9 @@
if (pi->conn_state & L2CAP_CONN_REMOTE_BUSY && pi->unacked_frames > 0)
__mod_retrans_timer();
+ spin_lock_bh(&pi->send_lock);
l2cap_ertm_send(sk);
+ spin_unlock_bh(&pi->send_lock);
if (!(pi->conn_state & L2CAP_CONN_LOCAL_BUSY) &&
pi->frames_sent == 0) {
@@ -3857,12 +3898,8 @@
if (rx_control & L2CAP_CTRL_FINAL) {
if (pi->conn_state & L2CAP_CONN_REJ_ACT)
pi->conn_state &= ~L2CAP_CONN_REJ_ACT;
- else {
- if (!skb_queue_empty(TX_QUEUE(sk)))
- sk->sk_send_head = TX_QUEUE(sk)->next;
- pi->next_tx_seq = pi->expected_ack_seq;
- l2cap_ertm_send(sk);
- }
+ else
+ l2cap_retransmit_frames(sk);
}
err = l2cap_push_rx_skb(sk, skb, rx_control);
@@ -3907,12 +3944,8 @@
if (pi->conn_state & L2CAP_CONN_REJ_ACT)
pi->conn_state &= ~L2CAP_CONN_REJ_ACT;
- else {
- if (!skb_queue_empty(TX_QUEUE(sk)))
- sk->sk_send_head = TX_QUEUE(sk)->next;
- pi->next_tx_seq = pi->expected_ack_seq;
- l2cap_ertm_send(sk);
- }
+ else
+ l2cap_retransmit_frames(sk);
} else {
if ((pi->conn_state & L2CAP_CONN_REMOTE_BUSY) &&
@@ -3920,10 +3953,13 @@
__mod_retrans_timer();
pi->conn_state &= ~L2CAP_CONN_REMOTE_BUSY;
- if (pi->conn_state & L2CAP_CONN_SREJ_SENT)
+ if (pi->conn_state & L2CAP_CONN_SREJ_SENT) {
l2cap_send_ack(pi);
- else
+ } else {
+ spin_lock_bh(&pi->send_lock);
l2cap_ertm_send(sk);
+ spin_unlock_bh(&pi->send_lock);
+ }
}
}
@@ -3940,17 +3976,10 @@
if (rx_control & L2CAP_CTRL_FINAL) {
if (pi->conn_state & L2CAP_CONN_REJ_ACT)
pi->conn_state &= ~L2CAP_CONN_REJ_ACT;
- else {
- if (!skb_queue_empty(TX_QUEUE(sk)))
- sk->sk_send_head = TX_QUEUE(sk)->next;
- pi->next_tx_seq = pi->expected_ack_seq;
- l2cap_ertm_send(sk);
- }
+ else
+ l2cap_retransmit_frames(sk);
} else {
- if (!skb_queue_empty(TX_QUEUE(sk)))
- sk->sk_send_head = TX_QUEUE(sk)->next;
- pi->next_tx_seq = pi->expected_ack_seq;
- l2cap_ertm_send(sk);
+ l2cap_retransmit_frames(sk);
if (pi->conn_state & L2CAP_CONN_WAIT_F)
pi->conn_state |= L2CAP_CONN_REJ_ACT;
@@ -3966,8 +3995,12 @@
if (rx_control & L2CAP_CTRL_POLL) {
pi->expected_ack_seq = tx_seq;
l2cap_drop_acked_frames(sk);
- l2cap_retransmit_frame(sk, tx_seq);
+ l2cap_retransmit_one_frame(sk, tx_seq);
+
+ spin_lock_bh(&pi->send_lock);
l2cap_ertm_send(sk);
+ spin_unlock_bh(&pi->send_lock);
+
if (pi->conn_state & L2CAP_CONN_WAIT_F) {
pi->srej_save_reqseq = tx_seq;
pi->conn_state |= L2CAP_CONN_SREJ_ACT;
@@ -3977,9 +4010,9 @@
pi->srej_save_reqseq == tx_seq)
pi->conn_state &= ~L2CAP_CONN_SREJ_ACT;
else
- l2cap_retransmit_frame(sk, tx_seq);
+ l2cap_retransmit_one_frame(sk, tx_seq);
} else {
- l2cap_retransmit_frame(sk, tx_seq);
+ l2cap_retransmit_one_frame(sk, tx_seq);
if (pi->conn_state & L2CAP_CONN_WAIT_F) {
pi->srej_save_reqseq = tx_seq;
pi->conn_state |= L2CAP_CONN_SREJ_ACT;
