Patch "netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
netfilter-ebtables-config_compat-don-t-trust-userland-offsets.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Florian Westphal <[email protected]>
Date: Mon, 19 Feb 2018 01:24:15 +0100
Subject: netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets

From: Florian Westphal <[email protected]>

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.

---
 net/bridge/netfilter/ebtables.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

@@ -2019,7 +2019,9 @@ static int ebt_size_mwt(struct compat_eb
 		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;
 	}
 

@@ -2076,6 +2078,15 @@ 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)
+			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;

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/netfilter-ipv6-fix-use-after-free-write-in-nf_nat_ipv6_manip_pkt.patch queue-3.18/netfilter-ebtables-config_compat-don-t-trust-userland-offsets.patch queue-3.18/netfilter-bridge-ebt_among-add-missing-match-size-checks.patch