netfilter: ebtables: compat: un-break 32bit setsockopt when no rules are present

[ Upstream commit 2035f3ff8eaa29cfb5c8e2160b0f6e85eeb21a95 ]

Unlike ip(6)tables ebtables only counts user-defined chains.

The effect is that a 32bit ebtables binary on a 64bit kernel can do
'ebtables -N FOO' only after adding at least one rule, else the request
fails with -EINVAL.

This is a similar fix as done in
3f1e53abff84 ("netfilter: ebtables: don't attempt to allocate 0-sized compat array").

Fixes: 7d7d7e02111e9 ("netfilter: compat: reject huge allocation requests")
Reported-by: Francesco Ruggeri <fruggeri@arista.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>

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 5e55cef..6693e20 100644 (file)
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2293,9 +2293,12 @@ static int compat_do_replace(struct net *net, void __user *user,
 
        xt_compat_lock(NFPROTO_BRIDGE);
 
-       ret = xt_compat_init_offsets(NFPROTO_BRIDGE, tmp.nentries);
-       if (ret < 0)
-               goto out_unlock;
+       if (tmp.nentries) {
+               ret = xt_compat_init_offsets(NFPROTO_BRIDGE, tmp.nentries);
+               if (ret < 0)
+                       goto out_unlock;
+       }
+
        ret = compat_copy_entries(entries_tmp, tmp.entries_size, &state);
        if (ret < 0)
                goto out_unlock;