From: Florian Westphal <fw@strlen.de>
Date: Thu, 8 Mar 2018 12:54:19 +0100
Subject: netfilter: ebtables: fix erroneous reject of last rule
Patch-mainline: v4.16-rc7
Git-commit: 932909d9b28d27e807ff8eecb68c7748f6701628
References: CVE-2018-1068 bsc#1085107
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>
Acked-by: Michal Kubecek <mkubecek@suse.cz>
---
net/bridge/netfilter/ebtables.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 601149463017..9b11e61c4b7e 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2121,8 +2121,12 @@ static int size_entry_mwt(struct ebt_entry *entry, const unsigned char *base,
* 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])
--
2.16.2