From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Gibson Subject: [PATCH 1/2] rtnetlink: Warn when interface's information won't fit in our packet Date: Thu, 24 Apr 2014 10:22:35 +1000 Message-ID: <1398298956-13084-2-git-send-email-david@gibson.dropbear.id.au> References: <1398298956-13084-1-git-send-email-david@gibson.dropbear.id.au> Cc: ssujith@cisco.com, neepatel@cisco.com, benve@cisco.com, davem@davemloft.net, ben@decadent.org.uk, govindarajulu90@gmail.com, gregory.v.rose@intel.com, David Gibson To: netdev@vger.kernel.org Return-path: Received: from ozlabs.org ([103.22.144.67]:33643 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751194AbaDXAWg (ORCPT ); Wed, 23 Apr 2014 20:22:36 -0400 In-Reply-To: <1398298956-13084-1-git-send-email-david@gibson.dropbear.id.au> Sender: netdev-owner@vger.kernel.org List-ID: Without IFLA_EXT_MASK specified, the information reported for a single interface in response to RTM_GETLINK is expected to fit within a netlink packet of NLMSG_GOODSIZE. If it doesn't, however, things will go badly wrong, When listing all interfaces, netlink_dump() will incorrectly treat -EMSGSIZE on the first message in a packet as the end of the listing and omit information for that interface and all subsequent ones. This can cause getifaddrs(3) to enter an infinite loop. This patch won't fix the problem, but it will WARN_ON() making it easier to track down what's going wrong. Signed-off-by: David Gibson --- net/core/rtnetlink.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index d4ff417..b5e384a 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -1198,6 +1198,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) struct hlist_head *head; struct nlattr *tb[IFLA_MAX+1]; u32 ext_filter_mask = 0; + int err; s_h = cb->args[0]; s_idx = cb->args[1]; @@ -1218,11 +1219,17 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) hlist_for_each_entry_rcu(dev, head, index_hlist) { if (idx < s_idx) goto cont; - if (rtnl_fill_ifinfo(skb, dev, RTM_NEWLINK, - NETLINK_CB(cb->skb).portid, - cb->nlh->nlmsg_seq, 0, - NLM_F_MULTI, - ext_filter_mask) <= 0) + err = rtnl_fill_ifinfo(skb, dev, RTM_NEWLINK, + NETLINK_CB(cb->skb).portid, + cb->nlh->nlmsg_seq, 0, + NLM_F_MULTI, + ext_filter_mask); + /* If we ran out of room on the first message, + * we're in trouble + */ + WARN_ON((err == -EMSGSIZE) && (skb->len == 0)); + + if (err <= 0) goto out; nl_dump_check_consistent(cb, nlmsg_hdr(skb)); -- 1.9.0