From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964992Ab1DNSRb (ORCPT ); Thu, 14 Apr 2011 14:17:31 -0400 Received: from mail.windriver.com ([147.11.1.11]:41813 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964857Ab1DNR6I (ORCPT ); Thu, 14 Apr 2011 13:58:08 -0400 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, Eric Dumazet , "David S. Miller" , Paul Gortmaker Subject: [34-longterm 147/209] filter: fix sk_filter rcu handling Date: Thu, 14 Apr 2011 13:55:05 -0400 Message-Id: <1302803767-9715-34-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1302803767-9715-1-git-send-email-paul.gortmaker@windriver.com> References: <1302803039-9400-1-git-send-email-paul.gortmaker@windriver.com> <1302803767-9715-1-git-send-email-paul.gortmaker@windriver.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet ===================================================================== | This is a commit scheduled for the next v2.6.34 longterm release. | | If you see a problem with using this for longterm, please comment.| ===================================================================== commit 46bcf14f44d8f31ecfdc8b6708ec15a3b33316d9 upstream 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 Signed-off-by: David S. Miller Signed-off-by: Paul Gortmaker --- include/net/sock.h | 4 +++- net/core/filter.c | 19 ++++++------------- 2 files changed, 9 insertions(+), 14 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index dc251e0..721c7b3 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1073,6 +1073,8 @@ 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 @@ -1083,7 +1085,7 @@ 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) diff --git a/net/core/filter.c b/net/core/filter.c index 3462e9d..2bc5376 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -472,23 +472,16 @@ int sk_chk_filter(struct sock_filter *filter, int flen) EXPORT_SYMBOL(sk_chk_filter); /** - * sk_filter_rcu_release: Release a socket filter by rcu_head + * sk_filter_release_rcu: 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) +void sk_filter_release_rcu(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); + kfree(fp); } +EXPORT_SYMBOL(sk_filter_release_rcu); /** * sk_attach_filter - attach a socket filter @@ -533,7 +526,7 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) rcu_read_unlock_bh(); if (old_fp) - sk_filter_delayed_uncharge(sk, old_fp); + sk_filter_uncharge(sk, old_fp); return 0; } EXPORT_SYMBOL_GPL(sk_attach_filter); @@ -547,7 +540,7 @@ int sk_detach_filter(struct sock *sk) filter = rcu_dereference_bh(sk->sk_filter); if (filter) { rcu_assign_pointer(sk->sk_filter, NULL); - sk_filter_delayed_uncharge(sk, filter); + sk_filter_uncharge(sk, filter); ret = 0; } rcu_read_unlock_bh(); -- 1.7.4.4