From e6b72ee88a56bcfe63f72e9c30766484c45bec72 Mon Sep 17 00:00:00 2001 From: Artem Savkov Date: Tue, 26 Sep 2017 18:35:45 +0200 Subject: [PATCH] netfilter: 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 Signed-off-by: Pablo Neira Ayuso --- 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 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..3b3dcf719e07 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 +1251,18 @@ 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: @@ -1276,7 +1277,7 @@ free_newinfo: free_table: kfree(table); out: - return ERR_PTR(ret); + return ret; } void ebt_unregister_table(struct net *net, struct ebt_table *table, -- 2.30.2