From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH] net: hold rtnl again in dump callbacks Date: Wed, 25 May 2011 19:34:04 +0200 Message-ID: <1306344844.11400.11.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev , Patrick McHardy , Stephen Hemminger To: David Miller Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:40650 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752441Ab1EYReK (ORCPT ); Wed, 25 May 2011 13:34:10 -0400 Received: by wya21 with SMTP id 21so5957893wya.19 for ; Wed, 25 May 2011 10:34:08 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: Commit e67f88dd12f6 (dont hold rtnl mutex during netlink dump callbacks) missed fact that rtnl_fill_ifinfo() must be called with rtnl held. Because of possible deadlocks between two mutexes (cb_mutex and rtnl), its not easy to solve this problem, so revert this part of the patch. It also forgot one rcu_read_unlock() in FIB dump_rules() Add one ASSERT_RTNL() in rtnl_fill_ifinfo() to remind us the rule. Signed-off-by: Eric Dumazet CC: Patrick McHardy CC: Stephen Hemminger --- I tried to solve this problem differently but failed. We need more preliminary steps. net/core/fib_rules.c | 1 + net/core/rtnetlink.c | 9 +++++++-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c index 3911586..008dc70 100644 --- a/net/core/fib_rules.c +++ b/net/core/fib_rules.c @@ -602,6 +602,7 @@ static int dump_rules(struct sk_buff *skb, struct netlink_callback *cb, skip: idx++; } + rcu_read_unlock(); cb->args[1] = idx; rules_ops_put(ops); diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index d1644e3..2d56cb9 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -850,6 +850,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev, struct nlattr *attr, *af_spec; struct rtnl_af_ops *af_ops; + ASSERT_RTNL(); nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags); if (nlh == NULL) return -EMSGSIZE; @@ -1876,6 +1877,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) int min_len; int family; int type; + int err; type = nlh->nlmsg_type; if (type > RTM_MAX) @@ -1902,8 +1904,11 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) if (dumpit == NULL) return -EOPNOTSUPP; + __rtnl_unlock(); rtnl = net->rtnl; - return netlink_dump_start(rtnl, skb, nlh, dumpit, NULL); + err = netlink_dump_start(rtnl, skb, nlh, dumpit, NULL); + rtnl_lock(); + return err; } memset(rta_buf, 0, (rtattr_max * sizeof(struct rtattr *))); @@ -1975,7 +1980,7 @@ static int __net_init rtnetlink_net_init(struct net *net) { struct sock *sk; sk = netlink_kernel_create(net, NETLINK_ROUTE, RTNLGRP_MAX, - rtnetlink_rcv, NULL, THIS_MODULE); + rtnetlink_rcv, &rtnl_mutex, THIS_MODULE); if (!sk) return -ENOMEM; net->rtnl = sk;