From 279230e0362486617bf1f53e46a114fce400099d Mon Sep 17 00:00:00 2001
From: Florian Westphal <fw@strlen.de>
Date: Mon, 19 Feb 2018 01:24:15 +0100
Subject: [PATCH] netfilter: ebtables: CONFIG_COMPAT: don't trust userland
offsets
commit b71812168571fa55e44cdd0254471331b9c4c4c6 upstream.
We need to make sure the offsets are not out of range of the
total size.
Also check that they are in ascending order.
The WARN_ON triggered by syzkaller (it sets panic_on_warn) is
changed to also bail out, no point in continuing parsing.
Briefly tested with simple ruleset of
-A INPUT --limit 1/s' --log
plus jump to custom chains using 32bit ebtables binary.
Reported-by: <syzbot+845a53d13171abf8bf29@syzkaller.appspotmail.com>
Bug: 77902350
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I01c7b86ed219c461113208c575148fe84f96317a
---
net/bridge/netfilter/ebtables.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 6651a7797d46..924af39089ea 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2010,7 +2010,9 @@ static int ebt_size_mwt(struct compat_ebt_entry_mwt *match32,
if (match_kern)
match_kern->match_size = ret;
- WARN_ON(type == EBT_COMPAT_TARGET && size_left);
+ if (WARN_ON(type == EBT_COMPAT_TARGET && size_left))
+ return -EINVAL;
+
match32 = (struct compat_ebt_entry_mwt *) buf;
}
@@ -2067,6 +2069,15 @@ 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)
+ return -EINVAL;
+ if (i == 0)
+ continue;
+ if (offsets[i-1] > offsets[i])
+ return -EINVAL;
+ }
+
for (i = 0, j = 1 ; j < 4 ; j++, i++) {
struct compat_ebt_entry_mwt *match32;
unsigned int size;
--
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