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>
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@ -38,7 +38,6 @@ struct skb_cb {
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struct in6_addr addr;
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struct in6_addr gw;
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struct l2cap_chan *chan;
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int status;
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};
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#define lowpan_cb(skb) ((struct skb_cb *)((skb)->cb))
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@ -485,7 +484,7 @@ static int send_pkt(struct l2cap_chan *chan, struct sk_buff *skb,
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}
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if (!err)
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err = lowpan_cb(skb)->status;
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err = (!chan->tx_credits ? -EAGAIN : 0);
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if (err < 0) {
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if (err == -EAGAIN)
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@ -880,26 +879,12 @@ static struct sk_buff *chan_alloc_skb_cb(struct l2cap_chan *chan,
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static void chan_suspend_cb(struct l2cap_chan *chan)
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{
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struct sk_buff *skb = chan->data;
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BT_DBG("chan %p conn %p skb %p", chan, chan->conn, skb);
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if (!skb)
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return;
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lowpan_cb(skb)->status = -EAGAIN;
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BT_DBG("chan %p suspend", chan);
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}
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static void chan_resume_cb(struct l2cap_chan *chan)
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{
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struct sk_buff *skb = chan->data;
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BT_DBG("chan %p conn %p skb %p", chan, chan->conn, skb);
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if (!skb)
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return;
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lowpan_cb(skb)->status = 0;
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BT_DBG("chan %p resume", chan);
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}
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static long chan_get_sndtimeo_cb(struct l2cap_chan *chan)
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