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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Florian Westphal" <fw@strlen.de>,
        "Pablo Neira Ayuso" <pablo@netfilter.org>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
Message-ID: <lsq.1528380321.733962665@decadent.org.uk>
Subject: [PATCH 3.16 016/410] netfilter: ebtables: fix erroneous reject of
 last rule
In-Reply-To: <lsq.1528380320.647747352@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Florian Westphal <fw@strlen.de>

commit 932909d9b28d27e807ff8eecb68c7748f6701628 upstream.

The last rule in the blob has next_entry offset that is same as total size.
This made "ebtables32 -A OUTPUT -d de:ad:be:ef:01:02" fail on 64 bit kernel.

Fixes: b71812168571fa ("netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 net/bridge/netfilter/ebtables.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2070,8 +2070,12 @@ static int size_entry_mwt(struct ebt_ent
 	 * offsets are relative to beginning of struct ebt_entry (i.e., 0).
 	 */
 	for (i = 0; i < 4 ; ++i) {
-		if (offsets[i] >= *total)
+		if (offsets[i] > *total)
 			return -EINVAL;
+
+		if (i < 3 && offsets[i] == *total)
+			return -EINVAL;
+
 		if (i == 0)
 			continue;
 		if (offsets[i-1] > offsets[i])