From: Artem Savkov <asavkov@redhat.com>
Date: Tue, 26 Sep 2017 18:35:45 +0200
Subject: netfilter: ebtables: fix race condition in frame_filter_net_init()
Patch-mainline: v4.14-rc5
Git-commit: e6b72ee88a56bcfe63f72e9c30766484c45bec72
References: bsc#1071929
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@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Michal Kubecek <mkubecek@suse.cz>
---
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, 19 insertions(+), 17 deletions(-)
diff --git a/include/linux/netfilter_bridge/ebtables.h b/include/linux/netfilter_bridge/ebtables.h
index e0cbf17af780..87e1caf81f04 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 f22ef7c21913..f29d9a424d2b 100644
--- a/net/bridge/netfilter/ebtable_filter.c
+++ b/net/bridge/netfilter/ebtable_filter.c
@@ -93,8 +93,8 @@ static struct nf_hook_ops ebt_ops_filter[] __read_mostly = {
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 2f7a4f314406..b5f96d56c5b6 100644
--- a/net/bridge/netfilter/ebtable_nat.c
+++ b/net/bridge/netfilter/ebtable_nat.c
@@ -93,8 +93,8 @@ static struct nf_hook_ops ebt_ops_nat[] __read_mostly = {
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 9c6e619f452b..621f75976dbd 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1178,9 +1178,8 @@ 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;
@@ -1192,7 +1191,7 @@ 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. */
@@ -1261,16 +1260,18 @@ 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);
+ WRITE_ONCE(*res, table);
+
if (!ops)
- return table;
+ return 0;
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 table;
+ return ret;
free_unlock:
mutex_unlock(&ebt_mutex);
free_chainstack:
@@ -1285,7 +1286,7 @@ 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,
--
2.15.1