From: Florian Westphal fw@strlen.de
[ Upstream commit e58a171d35e32e6e8c37cfe0e8a94406732a331f ]
We are not allowed to return an error at this point. Looking at the code it looks like ret is always 0 at this point, but its not.
t = find_table_lock(net, repl->name, &ret, &ebt_mutex);
... this can return a valid table, with ret != 0.
This bug causes update of table->private with the new blob, but then frees the blob right away in the caller.
Syzbot report:
BUG: KASAN: vmalloc-out-of-bounds in __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168 Read of size 4 at addr ffffc90005425000 by task kworker/u4:4/74 Workqueue: netns cleanup_net Call Trace: kasan_report+0xbf/0x1f0 mm/kasan/report.c:517 __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168 ebt_unregister_table+0x35/0x40 net/bridge/netfilter/ebtables.c:1372 ops_exit_list+0xb0/0x170 net/core/net_namespace.c:169 cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:613 ...
ip(6)tables appears to be ok (ret should be 0 at this point) but make this more obvious.
Fixes: c58dd2dd443c ("netfilter: Can't fail and free after table replacement") Reported-by: syzbot+f61594de72d6705aea03@syzkaller.appspotmail.com Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/bridge/netfilter/ebtables.c | 2 +- net/ipv4/netfilter/ip_tables.c | 3 +-- net/ipv6/netfilter/ip6_tables.c | 3 +-- 3 files changed, 3 insertions(+), 5 deletions(-)
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c index 16774559c52cb..a09b2fc11c80e 100644 --- a/net/bridge/netfilter/ebtables.c +++ b/net/bridge/netfilter/ebtables.c @@ -1090,7 +1090,7 @@ static int do_replace_finish(struct net *net, struct ebt_replace *repl,
audit_log_nfcfg(repl->name, AF_BRIDGE, repl->nentries, AUDIT_XT_OP_REPLACE, GFP_KERNEL); - return ret; + return 0;
free_unlock: mutex_unlock(&ebt_mutex); diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index 13acb687c19ab..91301dc3924a2 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -1044,7 +1044,6 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks, struct xt_counters *counters; struct ipt_entry *iter;
- ret = 0; counters = xt_counters_alloc(num_counters); if (!counters) { ret = -ENOMEM; @@ -1090,7 +1089,7 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks, net_warn_ratelimited("iptables: counters copy to user failed while replacing table\n"); } vfree(counters); - return ret; + return 0;
put_module: module_put(t->me); diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c index a579ea14a69b6..7ba68388d2e1f 100644 --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -1062,7 +1062,6 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks, struct xt_counters *counters; struct ip6t_entry *iter;
- ret = 0; counters = xt_counters_alloc(num_counters); if (!counters) { ret = -ENOMEM; @@ -1108,7 +1107,7 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks, net_warn_ratelimited("ip6tables: counters copy to user failed while replacing table\n"); } vfree(counters); - return ret; + return 0;
put_module: module_put(t->me);