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Subject[PATCH][MCAST]IPv6: doubt about ipv6_sk_mc_lock usage.
Hello.

I think ipv6_sk_mc_lock should protest both ipv6_mc_list and it's sflist. because they can are used by
inet6_mc_check(...) in softirq and be modified by ip6_mc_source(...) or ip6_mc_msfilter(...) simultaneity.
I also remove read_lock when traverse ipv6_mc_list, because it's protected by lock_sock(sk).

Regards

Signed-off-by: Yan Zheng <yanzheng@21cn.com>

Index: net/ipv6/mcast.c
====================================================================
--- linux-2.6.14/net/ipv6/mcast.c 2005-10-30 23:09:33.000000000 +0800
+++ linux/net/ipv6/mcast.c 2005-10-30 23:00:24.000000000 +0800
@@ -188,15 +188,12 @@ int ipv6_sock_mc_join(struct sock *sk, i
if (!ipv6_addr_is_multicast(addr))
return -EINVAL;

- read_lock_bh(&ipv6_sk_mc_lock);
for (mc_lst=np->ipv6_mc_list; mc_lst; mc_lst=mc_lst->next) {
if ((ifindex == 0 || mc_lst->ifindex == ifindex) &&
ipv6_addr_equal(&mc_lst->addr, addr)) {
- read_unlock_bh(&ipv6_sk_mc_lock);
return -EADDRINUSE;
}
}
- read_unlock_bh(&ipv6_sk_mc_lock);

mc_lst = sock_kmalloc(sk, sizeof(struct ipv6_mc_socklist), GFP_KERNEL);

@@ -379,7 +376,6 @@ int ip6_mc_source(int add, int omode, st

err = -EADDRNOTAVAIL;

- read_lock_bh(&ipv6_sk_mc_lock);
for (pmc=inet6->ipv6_mc_list; pmc; pmc=pmc->next) {
if (pgsr->gsr_interface && pmc->ifindex != pgsr->gsr_interface)
continue;
@@ -400,7 +396,7 @@ int ip6_mc_source(int add, int omode, st
/* allow mode switches for empty-set filters */
ip6_mc_add_src(idev, group, omode, 0, NULL, 0);
ip6_mc_del_src(idev, group, pmc->sfmode, 0, NULL, 0);
- pmc->sfmode = omode;
+ pmc->sfmode = omode; //need a write lock ?
}

psl = pmc->sflist;
@@ -425,10 +421,12 @@ int ip6_mc_source(int add, int omode, st

/* update the interface filter */
ip6_mc_del_src(idev, group, omode, 1, source, 1);
-
+
+ write_lock_bh(&ipv6_sk_mc_lock);
for (j=i+1; j<psl->sl_count; j++)
psl->sl_addr[j-1] = psl->sl_addr[j];
psl->sl_count--;
+ write_unlock_bh(&ipv6_sk_mc_lock);
err = 0;
goto done;
}
@@ -455,9 +453,12 @@ int ip6_mc_source(int add, int omode, st
if (psl) {
for (i=0; i<psl->sl_count; i++)
newpsl->sl_addr[i] = psl->sl_addr[i];
- sock_kfree_s(sk, psl, IP6_SFLSIZE(psl->sl_max));
}
+ write_lock_bh(&ipv6_sk_mc_lock);
+ if (psl)
+ sock_kfree_s(sk, psl, IP6_SFLSIZE(psl->sl_max));
pmc->sflist = psl = newpsl;
+ write_unlock_bh(&ipv6_sk_mc_lock);
}
rv = 1; /* > 0 for insert logic below if sl_count is 0 */
for (i=0; i<psl->sl_count; i++) {
@@ -467,15 +468,16 @@ int ip6_mc_source(int add, int omode, st
}
if (rv == 0) /* address already there is an error */
goto done;
+ write_lock_bh(&ipv6_sk_mc_lock);
for (j=psl->sl_count-1; j>=i; j--)
psl->sl_addr[j+1] = psl->sl_addr[j];
psl->sl_addr[i] = *source;
psl->sl_count++;
+ write_unlock_bh(&ipv6_sk_mc_lock);
err = 0;
/* update the interface list */
ip6_mc_add_src(idev, group, omode, 1, source, 1);
done:
- read_unlock_bh(&ipv6_sk_mc_lock);
read_unlock_bh(&idev->lock);
in6_dev_put(idev);
dev_put(dev);
@@ -548,14 +550,17 @@ int ip6_mc_msfilter(struct sock *sk, str
} else
newpsl = NULL;
psl = pmc->sflist;
- if (psl) {
+ if (psl)
(void) ip6_mc_del_src(idev, group, pmc->sfmode,
psl->sl_count, psl->sl_addr, 0);
- sock_kfree_s(sk, psl, IP6_SFLSIZE(psl->sl_max));
- } else
+ else
(void) ip6_mc_del_src(idev, group, pmc->sfmode, 0, NULL, 0);
+ write_lock_bh(&ipv6_sk_mc_lock);
+ if (psl)
+ sock_kfree_s(sk, psl, IP6_SFLSIZE(psl->sl_max));
pmc->sflist = newpsl;
pmc->sfmode = gsf->gf_fmode;
+ write_unlock_bh(&ipv6_sk_mc_lock);
err = 0;
done:
read_unlock_bh(&idev->lock);
-
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