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Date: Mon, 4 Jan 2010 16:51:09 -0200
From: Flavio Leitner <fbl@...close.org>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] igmp: fix ip_mc_sf_allow race
On Mon, Jan 04, 2010 at 02:07:03PM +0100, Eric Dumazet wrote:
> Le 04/01/2010 12:29, Flavio Leitner a écrit :
>
> > Then, I tried using call_rcu() to avoid the problem you are saying,
> > but when you stop the reproducer, sk_free() will warn printing
> > "optmem leakage.." because the rcu callback didn't run yet.
> >
> >
>
> This is probably because your call_rcu() callback was trying to call sock_kfree_s() ?
yes, correct.
>
> rtnl_unlock();
> call_rcu(&iml->lock, callback_func)
>
> callback_func()
> {
> sock_kfree_s(sk, iml, sizeof(*iml));
> }
>
>
>
> Take a look at sock_kfree_s() definition :
>
> void sock_kfree_s(struct sock *sk, void *mem, int size)
> {
> kfree(mem);
> atomic_sub(size, &sk->sk_omem_alloc);
> }
>
>
> You can certainly try :
>
> rtnl_unlock();
> atomic_sub(sizeof(*iml), sk->sk_omem_alloc);
> call_rcu(&iml->rcu, kfree);
>
> (immediate sk_omem_alloc handling, but deferred kfree())
Ok, below is the new version using call_rcu(). I'm still running my
tests here, so I'm planning to resubmit it later if this version is
okay with you.
thanks!
diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 724c27e..9cccd16 100644
--- a/include/linux/igmp.h
+++ b/include/linux/igmp.h
@@ -170,6 +170,7 @@ struct ip_mc_socklist {
struct ip_mreqn multi;
unsigned int sfmode; /* MCAST_{INCLUDE,EXCLUDE} */
struct ip_sf_socklist *sflist;
+ struct rcu_head rcu;
};
struct ip_sf_list {
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 76c0840..ed154db 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1799,7 +1799,7 @@ int ip_mc_join_group(struct sock *sk , struct ip_mreqn *imr)
iml->next = inet->mc_list;
iml->sflist = NULL;
iml->sfmode = MCAST_EXCLUDE;
- inet->mc_list = iml;
+ rcu_assign_pointer(inet->mc_list, iml);
ip_mc_inc_group(in_dev, addr);
err = 0;
done:
@@ -1825,6 +1825,17 @@ static int ip_mc_leave_src(struct sock *sk, struct ip_mc_socklist *iml,
return err;
}
+
+void ip_mc_socklist_reclaim(struct rcu_head *rp)
+{
+ struct ip_mc_socklist *iml;
+
+ iml = container_of(rp, struct ip_mc_socklist, rcu);
+ /* sk_omem_alloc should have been decreased by the caller*/
+ kfree(iml);
+}
+
+
/*
* Ask a socket to leave a group.
*/
@@ -1854,12 +1865,15 @@ int ip_mc_leave_group(struct sock *sk, struct ip_mreqn *imr)
(void) ip_mc_leave_src(sk, iml, in_dev);
- *imlp = iml->next;
+ rcu_assign_pointer(*imlp, iml->next);
if (in_dev)
ip_mc_dec_group(in_dev, group);
+
rtnl_unlock();
- sock_kfree_s(sk, iml, sizeof(*iml));
+ /* decrease mem now to avoid the memleak warning */
+ atomic_sub(sizeof(*iml), &sk->sk_omem_alloc);
+ call_rcu(&iml->rcu, ip_mc_socklist_reclaim);
return 0;
}
if (!in_dev)
@@ -2209,30 +2223,40 @@ int ip_mc_sf_allow(struct sock *sk, __be32 loc_addr, __be32 rmt_addr, int dif)
struct ip_mc_socklist *pmc;
struct ip_sf_socklist *psl;
int i;
+ int ret;
+ ret = 1;
if (!ipv4_is_multicast(loc_addr))
- return 1;
+ goto out;
- for (pmc=inet->mc_list; pmc; pmc=pmc->next) {
+ rcu_read_lock();
+ for (pmc=rcu_dereference(inet->mc_list); pmc; pmc=rcu_dereference(pmc->next)) {
if (pmc->multi.imr_multiaddr.s_addr == loc_addr &&
pmc->multi.imr_ifindex == dif)
break;
}
+ ret = inet->mc_all;
if (!pmc)
- return inet->mc_all;
+ goto unlock;
psl = pmc->sflist;
+ ret = (pmc->sfmode == MCAST_EXCLUDE);
if (!psl)
- return pmc->sfmode == MCAST_EXCLUDE;
+ goto unlock;
for (i=0; i<psl->sl_count; i++) {
if (psl->sl_addr[i] == rmt_addr)
break;
}
+ ret = 0;
if (pmc->sfmode == MCAST_INCLUDE && i >= psl->sl_count)
- return 0;
+ goto unlock;
if (pmc->sfmode == MCAST_EXCLUDE && i < psl->sl_count)
- return 0;
- return 1;
+ goto unlock;
+ ret = 1;
+unlock:
+ rcu_read_unlock();
+out:
+ return ret;
}
/*
@@ -2245,13 +2269,17 @@ void ip_mc_drop_socket(struct sock *sk)
struct ip_mc_socklist *iml;
struct net *net = sock_net(sk);
- if (inet->mc_list == NULL)
+ rcu_read_lock();
+ if (rcu_dereference(inet->mc_list) == NULL) {
+ rcu_read_unlock();
return;
+ }
+ rcu_read_unlock();
rtnl_lock();
- while ((iml = inet->mc_list) != NULL) {
+ while ((iml = rcu_dereference(inet->mc_list)) != NULL) {
struct in_device *in_dev;
- inet->mc_list = iml->next;
+ rcu_assign_pointer(inet->mc_list, iml->next);
in_dev = inetdev_by_index(net, iml->multi.imr_ifindex);
(void) ip_mc_leave_src(sk, iml, in_dev);
@@ -2259,7 +2287,9 @@ void ip_mc_drop_socket(struct sock *sk)
ip_mc_dec_group(in_dev, iml->multi.imr_multiaddr.s_addr);
in_dev_put(in_dev);
}
- sock_kfree_s(sk, iml, sizeof(*iml));
+ /* decrease mem now to avoid the memleak warning */
+ atomic_sub(sizeof(*iml), &sk->sk_omem_alloc);
+ call_rcu(&iml->rcu, ip_mc_socklist_reclaim);
}
rtnl_unlock();
}
--
1.6.2.3
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