From 47e958eac280c263397582d5581e868c3227a1bd Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Wed, 17 Oct 2007 21:22:42 -0700 Subject: [NET]: Fix the race between sk_filter_(de|at)tach and sk_clone() The proposed fix is to delay the reference counter decrement until the quiescent state pass. This will give sk_clone() a chance to get the reference on the cloned filter. Regular sk_filter_uncharge can happen from the sk_free() only and there's no need in delaying the put - the socket is dead anyway and is to be release itself. Signed-off-by: Pavel Emelyanov Signed-off-by: David S. Miller --- net/core/filter.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/core/filter.c b/net/core/filter.c index 54dddc92452d..1f0068eae501 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -386,6 +386,25 @@ int sk_chk_filter(struct sock_filter *filter, int flen) return (BPF_CLASS(filter[flen - 1].code) == BPF_RET) ? 0 : -EINVAL; } +/** + * sk_filter_rcu_release: Release a socket filter by rcu_head + * @rcu: rcu_head that contains the sk_filter to free + */ +static void sk_filter_rcu_release(struct rcu_head *rcu) +{ + struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu); + + sk_filter_release(fp); +} + +static void sk_filter_delayed_uncharge(struct sock *sk, struct sk_filter *fp) +{ + unsigned int size = sk_filter_len(fp); + + atomic_sub(size, &sk->sk_omem_alloc); + call_rcu_bh(&fp->rcu, sk_filter_rcu_release); +} + /** * sk_attach_filter - attach a socket filter * @fprog: the filter program @@ -428,7 +447,7 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) rcu_assign_pointer(sk->sk_filter, fp); rcu_read_unlock_bh(); - sk_filter_uncharge(sk, old_fp); + sk_filter_delayed_uncharge(sk, old_fp); return 0; } @@ -441,7 +460,7 @@ int sk_detach_filter(struct sock *sk) filter = rcu_dereference(sk->sk_filter); if (filter) { rcu_assign_pointer(sk->sk_filter, NULL); - sk_filter_uncharge(sk, filter); + sk_filter_delayed_uncharge(sk, filter); ret = 0; } rcu_read_unlock_bh(); -- cgit v1.2.1