Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755861Ab2KZRAh (ORCPT ); Mon, 26 Nov 2012 12:00:37 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:47041 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755840Ab2KZRAe (ORCPT ); Mon, 26 Nov 2012 12:00:34 -0500 From: Herton Ronaldo Krzesinski To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Pablo Neira Ayuso , Herton Ronaldo Krzesinski Subject: [PATCH 013/270] netfilter: nf_ct_expect: fix possible access to uninitialized timer Date: Mon, 26 Nov 2012 14:55:03 -0200 Message-Id: <1353949160-26803-14-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> References: <1353949160-26803-1-git-send-email-herton.krzesinski@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4519 Lines: 130 3.5.7u1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Pablo Neira Ayuso commit 2614f86490122bf51eb7c12ec73927f1900f4e7d upstream. In __nf_ct_expect_check, the function refresh_timer returns 1 if a matching expectation is found and its timer is successfully refreshed. This results in nf_ct_expect_related returning 0. Note that at this point: - the passed expectation is not inserted in the expectation table and its timer was not initialized, since we have refreshed one matching/existing expectation. - nf_ct_expect_alloc uses kmem_cache_alloc, so the expectation timer is in some undefined state just after the allocation, until it is appropriately initialized. This can be a problem for the SIP helper during the expectation addition: ... if (nf_ct_expect_related(rtp_exp) == 0) { if (nf_ct_expect_related(rtcp_exp) != 0) nf_ct_unexpect_related(rtp_exp); ... Note that nf_ct_expect_related(rtp_exp) may return 0 for the timer refresh case that is detailed above. Then, if nf_ct_unexpect_related(rtcp_exp) returns != 0, nf_ct_unexpect_related(rtp_exp) is called, which does: spin_lock_bh(&nf_conntrack_lock); if (del_timer(&exp->timeout)) { nf_ct_unlink_expect(exp); nf_ct_expect_put(exp); } spin_unlock_bh(&nf_conntrack_lock); Note that del_timer always returns false if the timer has been initialized. However, the timer was not initialized since setup_timer was not called, therefore, the expectation timer remains in some undefined state. If I'm not missing anything, this may lead to the removal an unexistent expectation. To fix this, the optimization that allows refreshing an expectation is removed. Now nf_conntrack_expect_related looks more consistent to me since it always add the expectation in case that it returns success. Thanks to Patrick McHardy for participating in the discussion of this patch. I think this may be the source of the problem described by: http://marc.info/?l=netfilter-devel&m=134073514719421&w=2 Reported-by: Rafal Fitt Acked-by: Patrick McHardy Signed-off-by: Pablo Neira Ayuso Acked-by: David S. Miller Signed-off-by: Herton Ronaldo Krzesinski --- net/netfilter/nf_conntrack_expect.c | 29 ++++++----------------------- 1 file changed, 6 insertions(+), 23 deletions(-) diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c index 45cf602..527651a 100644 --- a/net/netfilter/nf_conntrack_expect.c +++ b/net/netfilter/nf_conntrack_expect.c @@ -361,23 +361,6 @@ static void evict_oldest_expect(struct nf_conn *master, } } -static inline int refresh_timer(struct nf_conntrack_expect *i) -{ - struct nf_conn_help *master_help = nfct_help(i->master); - const struct nf_conntrack_expect_policy *p; - - if (!del_timer(&i->timeout)) - return 0; - - p = &rcu_dereference_protected( - master_help->helper, - lockdep_is_held(&nf_conntrack_lock) - )->expect_policy[i->class]; - i->timeout.expires = jiffies + p->timeout * HZ; - add_timer(&i->timeout); - return 1; -} - static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect) { const struct nf_conntrack_expect_policy *p; @@ -386,7 +369,7 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect) struct nf_conn_help *master_help = nfct_help(master); struct nf_conntrack_helper *helper; struct net *net = nf_ct_exp_net(expect); - struct hlist_node *n; + struct hlist_node *n, *next; unsigned int h; int ret = 1; @@ -395,12 +378,12 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect) goto out; } h = nf_ct_expect_dst_hash(&expect->tuple); - hlist_for_each_entry(i, n, &net->ct.expect_hash[h], hnode) { + hlist_for_each_entry_safe(i, n, next, &net->ct.expect_hash[h], hnode) { if (expect_matches(i, expect)) { - /* Refresh timer: if it's dying, ignore.. */ - if (refresh_timer(i)) { - ret = 0; - goto out; + if (del_timer(&i->timeout)) { + nf_ct_unlink_expect(i); + nf_ct_expect_put(i); + break; } } else if (expect_clash(i, expect)) { ret = -EBUSY; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/