can-raw: Fix skb_orphan_try handling

Commit fc6055a5ba31e2c14e36e8939f9bf2b6d586a7f5 (net: Introduce
skb_orphan_try()) allows an early orphan of the skb and takes care on
tx timestamping, which needs the sk-reference in the skb on driver level.
So does the can-raw socket, which has not been taken into account here.

The patch below adds a 'prevent_sk_orphan' bit in the skb tx shared info,
which fixes the problem discovered by Matthias Fuchs here:

      http://marc.info/?t=128030411900003&r=1&w=2

Even if it's not a primary tx timestamp topic it fits well into some skb
shared tx context. Or should be find a different place for the information to
protect the sk reference until it reaches the driver level?

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/can/raw.c b/net/can/raw.c
index ccfe633eec8..a10e3338f08 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -650,6 +650,10 @@ static int raw_sendmsg(struct kiocb *iocb, struct socket *sock,
         err = sock_tx_timestamp(msg, sk, skb_tx(skb));
         if (err < 0)
                 goto free_skb;
+
+        /* to be able to check the received tx sock reference in raw_rcv() */
+        skb_tx(skb)->prevent_sk_orphan = 1;
+
         skb->dev = dev;
         skb->sk  = sk;