Bluetooth: 6lowpan: fix use after free in chan_suspend/resume
A status field in the skb_cb struct was storing a channel status
based on channel suspend/resume events. This stored status was
then used to return EAGAIN if there were packet sending issues
in snd_pkt().
The issue is that the skb has been freed by the time the callback
to 6lowpan's suspend/resume was called. So, this generates a
"use after free" issue that was noticed while running kernel tests
with KASAN debug enabled.
Let's eliminate the status field entirely as we can use the channel
tx_credits to indicate whether we should return EAGAIN when handling
packets.
Signed-off-by: Michael Scott <michael.scott@linaro.org>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index 6ae51e8..b39da8d 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -38,7 +38,6 @@ struct skb_cb {
struct in6_addr addr;
struct in6_addr gw;
struct l2cap_chan *chan;
- int status;
};
#define lowpan_cb(skb) ((struct skb_cb *)((skb)->cb))
@@ -485,7 +484,7 @@ static int send_pkt(struct l2cap_chan *chan, struct sk_buff *skb,
}
if (!err)
- err = lowpan_cb(skb)->status;
+ err = (!chan->tx_credits ? -EAGAIN : 0);
if (err < 0) {
if (err == -EAGAIN)
@@ -880,26 +879,12 @@ static struct sk_buff *chan_alloc_skb_cb(struct l2cap_chan *chan,
static void chan_suspend_cb(struct l2cap_chan *chan)
{
- struct sk_buff *skb = chan->data;
-
- BT_DBG("chan %p conn %p skb %p", chan, chan->conn, skb);
-
- if (!skb)
- return;
-
- lowpan_cb(skb)->status = -EAGAIN;
+ BT_DBG("chan %p suspend", chan);
}
static void chan_resume_cb(struct l2cap_chan *chan)
{
- struct sk_buff *skb = chan->data;
-
- BT_DBG("chan %p conn %p skb %p", chan, chan->conn, skb);
-
- if (!skb)
- return;
-
- lowpan_cb(skb)->status = 0;
+ BT_DBG("chan %p resume", chan);
}
static long chan_get_sndtimeo_cb(struct l2cap_chan *chan)