[PATCH net-next 0/2] ipv6: addrconf: make two more doit functions not use rtnl mutex

[PATCH net-next 0/2] ipv6: addrconf: make two more doit functions not use rtnl mutex

[Florian Westphal]

ipv6 RTM_GETNETCONF and RTM_GETADDR don't seem to require strict
serialization via rtnl mutex, so switch both to DOIT_UNLOCKED and increment
device reference counts instead.

Alternative would be to use rcu which would need some minor
code re-arrangements (we can't use GFP_ATOMIC for buffer allocation in that
case).

 addrconf.c |   38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

[PATCH net-next 1/2] ipv6: addrconf: don't use rtnl mutex in RTM_GETNETCONF

[Florian Westphal]

Instead of relying on rtnl mutex bump device reference count.
After this change, values reported can change in parallel, but thats not
much different from current state, as anyone can change the settings
right after rtnl_unlock (and before userspace processed reply).

While at it, switch to GFP_KERNEL allocation.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/ipv6/addrconf.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index d9f6226694eb..5207f567ef28 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -616,23 +616,23 @@ static int inet6_netconf_get_devconf(struct sk_buff *in_skb,
 {
 	struct net *net = sock_net(in_skb->sk);
 	struct nlattr *tb[NETCONFA_MAX+1];
+	struct inet6_dev *in6_dev = NULL;
+	struct net_device *dev = NULL;
 	struct netconfmsg *ncm;
 	struct sk_buff *skb;
 	struct ipv6_devconf *devconf;
-	struct inet6_dev *in6_dev;
-	struct net_device *dev;
 	int ifindex;
 	int err;
 
 	err = nlmsg_parse(nlh, sizeof(*ncm), tb, NETCONFA_MAX,
 			  devconf_ipv6_policy, extack);
 	if (err < 0)
-		goto errout;
+		return err;
 
-	err = -EINVAL;
 	if (!tb[NETCONFA_IFINDEX])
-		goto errout;
+		return -EINVAL;
 
+	err = -EINVAL;
 	ifindex = nla_get_s32(tb[NETCONFA_IFINDEX]);
 	switch (ifindex) {
 	case NETCONFA_IFINDEX_ALL:
@@ -642,10 +642,10 @@ static int inet6_netconf_get_devconf(struct sk_buff *in_skb,
 		devconf = net->ipv6.devconf_dflt;
 		break;
 	default:
-		dev = __dev_get_by_index(net, ifindex);
+		dev = dev_get_by_index(net, ifindex);
 		if (!dev)
-			goto errout;
-		in6_dev = __in6_dev_get(dev);
+			return -EINVAL;
+		in6_dev = in6_dev_get(dev);
 		if (!in6_dev)
 			goto errout;
 		devconf = &in6_dev->cnf;
@@ -653,7 +653,7 @@ static int inet6_netconf_get_devconf(struct sk_buff *in_skb,
 	}
 
 	err = -ENOBUFS;
-	skb = nlmsg_new(inet6_netconf_msgsize_devconf(NETCONFA_ALL), GFP_ATOMIC);
+	skb = nlmsg_new(inet6_netconf_msgsize_devconf(NETCONFA_ALL), GFP_KERNEL);
 	if (!skb)
 		goto errout;
 
@@ -669,6 +669,10 @@ static int inet6_netconf_get_devconf(struct sk_buff *in_skb,
 	}
 	err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
 errout:
+	if (in6_dev)
+		in6_dev_put(in6_dev);
+	if (dev)
+		dev_put(dev);
 	return err;
 }
 
@@ -6570,7 +6574,7 @@ int __init addrconf_init(void)
 	__rtnl_register(PF_INET6, RTM_GETANYCAST, NULL,
 			inet6_dump_ifacaddr, 0);
 	__rtnl_register(PF_INET6, RTM_GETNETCONF, inet6_netconf_get_devconf,
-			inet6_netconf_dump_devconf, 0);
+			inet6_netconf_dump_devconf, RTNL_FLAG_DOIT_UNLOCKED);
 
 	ipv6_addr_label_rtnl_register();
 
-- 
2.13.6

[PATCH net-next 2/2] ipv6: addrconf: don't use rtnl mutex in RTM_GETADDR

[Florian Westphal]

Similar to the previous patch, use the device lookup functions
that bump device refcount and flag this as DOIT_UNLOCKED to avoid
rtnl mutex.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/ipv6/addrconf.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 5207f567ef28..4603aa488f4f 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4890,17 +4890,15 @@ static int inet6_rtm_getaddr(struct sk_buff *in_skb, struct nlmsghdr *nlh,
 	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, ifa_ipv6_policy,
 			  extack);
 	if (err < 0)
-		goto errout;
+		return err;
 
 	addr = extract_addr(tb[IFA_ADDRESS], tb[IFA_LOCAL], &peer);
-	if (!addr) {
-		err = -EINVAL;
-		goto errout;
-	}
+	if (!addr)
+		return -EINVAL;
 
 	ifm = nlmsg_data(nlh);
 	if (ifm->ifa_index)
-		dev = __dev_get_by_index(net, ifm->ifa_index);
+		dev = dev_get_by_index(net, ifm->ifa_index);
 
 	ifa = ipv6_get_ifaddr(net, addr, dev, 1);
 	if (!ifa) {
@@ -4926,6 +4924,8 @@ static int inet6_rtm_getaddr(struct sk_buff *in_skb, struct nlmsghdr *nlh,
 errout_ifa:
 	in6_ifa_put(ifa);
 errout:
+	if (dev)
+		dev_put(dev);
 	return err;
 }
 
@@ -6568,7 +6568,7 @@ int __init addrconf_init(void)
 	__rtnl_register(PF_INET6, RTM_NEWADDR, inet6_rtm_newaddr, NULL, 0);
 	__rtnl_register(PF_INET6, RTM_DELADDR, inet6_rtm_deladdr, NULL, 0);
 	__rtnl_register(PF_INET6, RTM_GETADDR, inet6_rtm_getaddr,
-			inet6_dump_ifaddr, 0);
+			inet6_dump_ifaddr, RTNL_FLAG_DOIT_UNLOCKED);
 	__rtnl_register(PF_INET6, RTM_GETMULTICAST, NULL,
 			inet6_dump_ifmcaddr, 0);
 	__rtnl_register(PF_INET6, RTM_GETANYCAST, NULL,
-- 
2.13.6

Re: [PATCH net-next 1/2] ipv6: addrconf: don't use rtnl mutex in RTM_GETNETCONF

[David Miller]

From: Florian Westphal <fw@strlen.de>
Date: Wed, 11 Oct 2017 10:28:00 +0200

> Instead of relying on rtnl mutex bump device reference count.
> After this change, values reported can change in parallel, but thats not
> much different from current state, as anyone can change the settings
> right after rtnl_unlock (and before userspace processed reply).
> 
> While at it, switch to GFP_KERNEL allocation.
> 
> Signed-off-by: Florian Westphal <fw@strlen.de>

Applied.

Re: [PATCH net-next 2/2] ipv6: addrconf: don't use rtnl mutex in RTM_GETADDR

[David Miller]

From: Florian Westphal <fw@strlen.de>
Date: Wed, 11 Oct 2017 10:28:01 +0200

> Similar to the previous patch, use the device lookup functions
> that bump device refcount and flag this as DOIT_UNLOCKED to avoid
> rtnl mutex.
> 
> Signed-off-by: Florian Westphal <fw@strlen.de>

Applied.