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>
diff --git a/include/net/sock.h b/include/net/sock.h
index a6338d0..659d968d9 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1155,6 +1155,8 @@
/* Initialise core socket variables */
extern void sock_init_data(struct socket *sock, struct sock *sk);
+extern void sk_filter_release_rcu(struct rcu_head *rcu);
+
/**
* sk_filter_release - release a socket filter
* @fp: filter to remove
@@ -1165,7 +1167,7 @@
static inline void sk_filter_release(struct sk_filter *fp)
{
if (atomic_dec_and_test(&fp->refcnt))
- kfree(fp);
+ call_rcu_bh(&fp->rcu, sk_filter_release_rcu);
}
static inline void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)