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filter: fix sk_filter rcu handling

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Pavel Emelyanov tried to fix a race between sk_filter_(de|at)tach and
sk_clone() in commit 47e958eac2

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>
This commit is contained in:
Eric Dumazet
2010-12-06 09:29:43 -08:00
committed by David S. Miller
parent e7dfc8dbdf
commit 46bcf14f44
2 changed files with 9 additions and 14 deletions
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4
include/net/sock.h
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@ -1155,6 +1155,8 @@ extern void sk_common_release(struct sock *sk);
/* 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 @@ extern void sock_init_data(struct socket *sock, struct sock *sk);
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)