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Date: Tue, 26 Sep 2017 17:39:23 +0200
From: Artem Savkov <asavkov@...hat.com>
To: Florian Westphal <fw@...len.de>
Cc: Pablo Neira Ayuso <pablo@...filter.org>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
Artem Savkov <asavkov@...hat.com>
Subject: [PATCH v2] ebtables: fix race condition in frame_filter_net_init()
It is possible for ebt_in_hook to be triggered before ebt_table is assigned
resulting in a NULL-pointer dereference. Make sure hooks are
registered as the last step.
Fixes: aee12a0a3727 ebtables: remove nf_hook_register usage
Signed-off-by: Artem Savkov <asavkov@...hat.com>
---
include/linux/netfilter_bridge/ebtables.h | 7 ++++---
net/bridge/netfilter/ebtable_broute.c | 4 ++--
net/bridge/netfilter/ebtable_filter.c | 4 ++--
net/bridge/netfilter/ebtable_nat.c | 4 ++--
net/bridge/netfilter/ebtables.c | 17 ++++++++---------
5 files changed, 18 insertions(+), 18 deletions(-)
diff --git a/include/linux/netfilter_bridge/ebtables.h b/include/linux/netfilter_bridge/ebtables.h
index 2c2a5514b0df..528b24c78308 100644
--- a/include/linux/netfilter_bridge/ebtables.h
+++ b/include/linux/netfilter_bridge/ebtables.h
@@ -108,9 +108,10 @@ struct ebt_table {
#define EBT_ALIGN(s) (((s) + (__alignof__(struct _xt_align)-1)) & \
~(__alignof__(struct _xt_align)-1))
-extern struct ebt_table *ebt_register_table(struct net *net,
- const struct ebt_table *table,
- const struct nf_hook_ops *);
+extern int ebt_register_table(struct net *net,
+ const struct ebt_table *table,
+ const struct nf_hook_ops *ops,
+ struct ebt_table **res);
extern void ebt_unregister_table(struct net *net, struct ebt_table *table,
const struct nf_hook_ops *);
extern unsigned int ebt_do_table(struct sk_buff *skb,
diff --git a/net/bridge/netfilter/ebtable_broute.c b/net/bridge/netfilter/ebtable_broute.c
index 2585b100ebbb..276b60262981 100644
--- a/net/bridge/netfilter/ebtable_broute.c
+++ b/net/bridge/netfilter/ebtable_broute.c
@@ -65,8 +65,8 @@ static int ebt_broute(struct sk_buff *skb)
static int __net_init broute_net_init(struct net *net)
{
- net->xt.broute_table = ebt_register_table(net, &broute_table, NULL);
- return PTR_ERR_OR_ZERO(net->xt.broute_table);
+ return ebt_register_table(net, &broute_table, NULL,
+ &net->xt.broute_table);
}
static void __net_exit broute_net_exit(struct net *net)
diff --git a/net/bridge/netfilter/ebtable_filter.c b/net/bridge/netfilter/ebtable_filter.c
index 45a00dbdbcad..c41da5fac84f 100644
--- a/net/bridge/netfilter/ebtable_filter.c
+++ b/net/bridge/netfilter/ebtable_filter.c
@@ -93,8 +93,8 @@ static const struct nf_hook_ops ebt_ops_filter[] = {
static int __net_init frame_filter_net_init(struct net *net)
{
- net->xt.frame_filter = ebt_register_table(net, &frame_filter, ebt_ops_filter);
- return PTR_ERR_OR_ZERO(net->xt.frame_filter);
+ return ebt_register_table(net, &frame_filter, ebt_ops_filter,
+ &net->xt.frame_filter);
}
static void __net_exit frame_filter_net_exit(struct net *net)
diff --git a/net/bridge/netfilter/ebtable_nat.c b/net/bridge/netfilter/ebtable_nat.c
index 57cd5bb154e7..08df7406ecb3 100644
--- a/net/bridge/netfilter/ebtable_nat.c
+++ b/net/bridge/netfilter/ebtable_nat.c
@@ -93,8 +93,8 @@ static const struct nf_hook_ops ebt_ops_nat[] = {
static int __net_init frame_nat_net_init(struct net *net)
{
- net->xt.frame_nat = ebt_register_table(net, &frame_nat, ebt_ops_nat);
- return PTR_ERR_OR_ZERO(net->xt.frame_nat);
+ return ebt_register_table(net, &frame_nat, ebt_ops_nat,
+ &net->xt.frame_nat);
}
static void __net_exit frame_nat_net_exit(struct net *net)
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 83951f978445..aa81afe81f23 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1169,9 +1169,8 @@ static void __ebt_unregister_table(struct net *net, struct ebt_table *table)
kfree(table);
}
-struct ebt_table *
-ebt_register_table(struct net *net, const struct ebt_table *input_table,
- const struct nf_hook_ops *ops)
+int ebt_register_table(struct net *net, const struct ebt_table *input_table,
+ const struct nf_hook_ops *ops, struct ebt_table **res)
{
struct ebt_table_info *newinfo;
struct ebt_table *t, *table;
@@ -1183,7 +1182,7 @@ ebt_register_table(struct net *net, const struct ebt_table *input_table,
repl->entries == NULL || repl->entries_size == 0 ||
repl->counters != NULL || input_table->private != NULL) {
BUGPRINT("Bad table data for ebt_register_table!!!\n");
- return ERR_PTR(-EINVAL);
+ return -EINVAL;
}
/* Don't add one table to multiple lists. */
@@ -1252,16 +1251,16 @@ ebt_register_table(struct net *net, const struct ebt_table *input_table,
list_add(&table->list, &net->xt.tables[NFPROTO_BRIDGE]);
mutex_unlock(&ebt_mutex);
- if (!ops)
- return table;
+ WRITE_ONCE(*res, table);
ret = nf_register_net_hooks(net, ops, hweight32(table->valid_hooks));
if (ret) {
__ebt_unregister_table(net, table);
- return ERR_PTR(ret);
+ *res = NULL;
+ return ret;
}
- return table;
+ return 0;
free_unlock:
mutex_unlock(&ebt_mutex);
free_chainstack:
@@ -1276,7 +1275,7 @@ ebt_register_table(struct net *net, const struct ebt_table *input_table,
free_table:
kfree(table);
out:
- return ERR_PTR(ret);
+ return ret;
}
void ebt_unregister_table(struct net *net, struct ebt_table *table,
--
2.13.5
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