| Message ID | 20230217222006.169428-1-fw@strlen.de |
|---|---|
| State | Accepted |
| Delegated to: | Pablo Neira |
| Headers | show |
| Series | [nf] ebtables: fix table blob use-after-free | expand |
On Fri, Feb 17, 2023 at 11:20:06PM +0100, Florian Westphal wrote: > 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. Applied, thanks
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c index ce5dfa3babd2..757ec46fc45a 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 2ed7c58b471a..aae5fd51dfd7 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -1045,7 +1045,6 @@ __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; @@ -1091,7 +1090,7 @@ __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 2d816277f2c5..ac902f7bca47 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);
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> --- 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(-)