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netfilter: ebtables: fix table blob use-after-free
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: c58dd2dd44
("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>
This commit is contained in:
parent
efb056e5f1
commit
e58a171d35
@ -1090,7 +1090,7 @@ static int do_replace_finish(struct net *net, struct ebt_replace *repl,
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audit_log_nfcfg(repl->name, AF_BRIDGE, repl->nentries,
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AUDIT_XT_OP_REPLACE, GFP_KERNEL);
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return ret;
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return 0;
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free_unlock:
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mutex_unlock(&ebt_mutex);
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@ -1045,7 +1045,6 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
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struct xt_counters *counters;
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struct ipt_entry *iter;
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ret = 0;
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counters = xt_counters_alloc(num_counters);
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if (!counters) {
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ret = -ENOMEM;
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@ -1091,7 +1090,7 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
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net_warn_ratelimited("iptables: counters copy to user failed while replacing table\n");
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}
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vfree(counters);
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return ret;
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return 0;
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put_module:
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module_put(t->me);
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@ -1062,7 +1062,6 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
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struct xt_counters *counters;
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struct ip6t_entry *iter;
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ret = 0;
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counters = xt_counters_alloc(num_counters);
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if (!counters) {
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ret = -ENOMEM;
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@ -1108,7 +1107,7 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
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net_warn_ratelimited("ip6tables: counters copy to user failed while replacing table\n");
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}
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vfree(counters);
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return ret;
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return 0;
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put_module:
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module_put(t->me);
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