linux-kernel - [PATCH 3.2 005/153] netfilter: ebtables: fix erroneous reject of last rule

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Message-ID: <lsq.1527677561.711329105@decadent.org.uk>
Date:   Wed, 30 May 2018 11:52:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Pablo Neira Ayuso" <pablo@...filter.org>,
        "Florian Westphal" <fw@...len.de>
Subject: [PATCH 3.2 005/153] netfilter: ebtables: fix erroneous reject of
 last rule

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

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

From: Florian Westphal <fw@...len.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@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Ben Hutchings <ben@...adent.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
@@ -2064,8 +2064,12 @@ 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])