netdev - [PATCH nf] netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20180219002415.18461-1-fw@strlen.de>
Date:   Mon, 19 Feb 2018 01:24:15 +0100
From:   Florian Westphal <fw@...len.de>
To:     <netfilter-devel@...r.kernel.org>
Cc:     syzkaller-bugs@...glegroups.com, bridge@...ts.linux-foundation.org,
        netdev@...r.kernel.org, Florian Westphal <fw@...len.de>
Subject: [PATCH nf] netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets

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@...kaller.appspotmail.com>
Signed-off-by: Florian Westphal <fw@...len.de>
---
 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 02c4b409d317..3f536c7a3354 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2053,7 +2053,9 @@ 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;
 	}
 
@@ -2109,6 +2111,15 @@ 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;
-- 
2.16.1