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Date: Sat, 30 Aug 2014 12:58:21 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc: Cong Wang <cwang@...pensource.com>,
Tommi Rantala <tt.rantala@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
James Morris <jmorris@...ei.org>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Patrick McHardy <kaber@...sh.net>,
netdev <netdev@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>, trinity@...r.kernel.org,
Dave Jones <davej@...hat.com>
Subject: Re: RTNL: assertion failed at net/ipv6/addrconf.c (1699)
Hello,
2014-08-30, 03:51:29 +0200, Hannes Frederic Sowa wrote:
> Hi Sabrina,
>
> [...]
>
> Sorry, just had time to look at this.
>
> The reason is not to have list corruption but that the calls down to
> ndo_set_rx_mode expect rtnl to be locked by the drivers. Filter lists
> are locked by addr_list_lock and that's why I think we never saw any
> problems with that, but drivers expect rtnl locked for those calls.
>
> But this problem also affects multicast join, so patch seems incomplete
> to me (and for that matter ssm multicast join, too).
>
> Also rtnl_lock and rcu_read_lock compose in that order, so we don't need
> to change dev_get_by_flags, but as this is the only user it sure is
> possible. RCU locked version is just easier composeable, so I wouldn't
> touch that if needed in future, just also take rcu lock as before.
>
> So just adding rtnl_lock add appropriate places seems to be ok to me,
> but still need to review parts of the ssm code.
>
> Also we should move ASSERT_RTNL checks from addrconf_join_solict to
> ipv6_dev_mc_inc/dec.
>
> Thanks,
> Hannes
Thanks for explaining.
I had a look at what you suggested.
So, for anycast, on top of the previous patch, we'd have:
---
diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
index 210183244689..61dd3046b804 100644
--- a/net/ipv6/anycast.c
+++ b/net/ipv6/anycast.c
static void aca_put(struct ifacaddr6 *ac)
@@ -233,6 +235,8 @@ int ipv6_dev_ac_inc(struct net_device *dev, const struct in6_addr *addr)
struct rt6_info *rt;
int err;
+ ASSERT_RTNL();
+
idev = in6_dev_get(dev);
if (idev == NULL)
@@ -302,6 +306,8 @@ int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr)
{
struct ifacaddr6 *aca, *prev_aca;
+ ASSERT_RTNL();
+
write_lock_bh(&idev->lock);
prev_aca = NULL;
for (aca = idev->ac_list; aca; aca = aca->aca_next) {
@@ -336,6 +342,8 @@ static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr)
{
struct inet6_dev *idev = __in6_dev_get(dev);
+ ASSERT_RTNL();
+
if (idev == NULL)
return -ENODEV;
return __ipv6_dev_ac_dec(idev, addr);
---
And for multicast:
- locking order in the patch below: rtnl -> rcu -> ipv6_sk_mc_lock
- ipv6_sock_mc_join: maybe move all the _unlock()'s together at the end of the function
- do we need to modify rcu_dereference_protected in ipv6_sock_mc_drop/ipv6_sock_mc_close
- I had a look at the other codepaths that call ipv6_dev_mc_inc/dec
- ipv6_mc_destroy_dev, dev_forward_change, ipv6_add_dev,
addrconf_join_solict -- all take rtnl or already have an
ASSERT_RTNL()
- pndisc_destructor, called from pneigh_ifdown/pneigh_delete
- pndisc_constructor, called from pneigh_lookup -- pneigh_lookup
has ASSERT_RTNL(), but pneigh_lookup is called from ip6_forward and
ndisc_recv_na
- (hope I didn't miss any callers)
As far as I could see, apart maybe from pndisc_constructor, it seems
okay, but I'd like to hear your comments.
Current modifications:
---
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 70881795da96..d73ac1ef65f2 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -172,6 +172,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
mc_lst->next = NULL;
mc_lst->addr = *addr;
+ rtnl_lock();
rcu_read_lock();
if (ifindex == 0) {
struct rt6_info *rt;
@@ -185,6 +186,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
if (dev == NULL) {
rcu_read_unlock();
+ rtnl_unlock();
sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
return -ENODEV;
}
@@ -202,6 +204,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
if (err) {
rcu_read_unlock();
+ rtnl_unlock();
sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
return err;
}
@@ -212,6 +215,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
spin_unlock(&ipv6_sk_mc_lock);
rcu_read_unlock();
+ rtnl_unlock();
return 0;
}
@@ -229,6 +233,7 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
if (!ipv6_addr_is_multicast(addr))
return -EINVAL;
+ rtnl_lock();
spin_lock(&ipv6_sk_mc_lock);
for (lnk = &np->ipv6_mc_list;
(mc_lst = rcu_dereference_protected(*lnk,
@@ -252,12 +257,15 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
} else
(void) ip6_mc_leave_src(sk, mc_lst, NULL);
rcu_read_unlock();
+ rtnl_unlock();
+
atomic_sub(sizeof(*mc_lst), &sk->sk_omem_alloc);
kfree_rcu(mc_lst, rcu);
return 0;
}
}
spin_unlock(&ipv6_sk_mc_lock);
+ rtnl_unlock();
return -EADDRNOTAVAIL;
}
@@ -302,6 +310,7 @@ void ipv6_sock_mc_close(struct sock *sk)
if (!rcu_access_pointer(np->ipv6_mc_list))
return;
+ rtnl_lock();
spin_lock(&ipv6_sk_mc_lock);
while ((mc_lst = rcu_dereference_protected(np->ipv6_mc_list,
lockdep_is_held(&ipv6_sk_mc_lock))) != NULL) {
@@ -328,6 +337,7 @@ void ipv6_sock_mc_close(struct sock *sk)
spin_lock(&ipv6_sk_mc_lock);
}
spin_unlock(&ipv6_sk_mc_lock);
+ rtnl_unlock();
}
int ip6_mc_source(int add, int omode, struct sock *sk,
@@ -845,6 +855,8 @@ int ipv6_dev_mc_inc(struct net_device *dev, const struct in6_addr *addr)
struct ifmcaddr6 *mc;
struct inet6_dev *idev;
+ ASSERT_RTNL();
+
/* we need to take a reference on idev */
idev = in6_dev_get(dev);
@@ -916,6 +928,8 @@ int __ipv6_dev_mc_dec(struct inet6_dev *idev, const struct in6_addr *addr)
{
struct ifmcaddr6 *ma, **map;
+ ASSERT_RTNL();
+
write_lock_bh(&idev->lock);
for (map = &idev->mc_list; (ma = *map) != NULL; map = &ma->next) {
if (ipv6_addr_equal(&ma->mca_addr, addr)) {
@@ -942,6 +956,8 @@ int ipv6_dev_mc_dec(struct net_device *dev, const struct in6_addr *addr)
struct inet6_dev *idev;
int err;
+ ASSERT_RTNL();
+
rcu_read_lock();
idev = __in6_dev_get(dev);
---
Thanks,
--
Sabrina
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