tree 4d2a200387242e1ed2d95ccd367c77750379e8cc
parent e7dfc8dbdf9a7fa1ef04c63100a71f4102b82ed3
author Eric Dumazet <eric.dumazet@gmail.com> 1291656583 -0800
committer David S. Miller <davem@davemloft.net> 1291656583 -0800

filter: fix sk_filter rcu handling

Pavel Emelyanov tried to fix a race between sk_filter_(de|at)tach and
sk_clone() in commit 47e958eac280c263397

Problem is we can have several clones sharing a common sk_filter, and
these clones might want to sk_filter_attach() their own filters at the
same time, and can overwrite old_filter->rcu, corrupting RCU queues.

We can not use filter->rcu without being sure no other thread could do
the same thing.

Switch code to a more conventional ref-counting technique : Do the
atomic decrement immediately and queue one rcu call back when last
reference is released.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>