linux-kernel - [PATCH 4.20 036/171] netfilter: ebtables: compat: un-break 32bit setsockopt when no rules are present

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Message-Id: <20190312170351.167906120@linuxfoundation.org>
Date:   Tue, 12 Mar 2019 10:06:56 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Francesco Ruggeri <fruggeri@...sta.com>,
        Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.20 036/171] netfilter: ebtables: compat: un-break 32bit setsockopt when no rules are present

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ 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@...sta.com>
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/bridge/netfilter/ebtables.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 5e55cef0cec3..6693e209efe8 100644
--- 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;
-- 
2.19.1