From dcafeb49b2538cc7118cb64f62c685980c106b48 Mon Sep 17 00:00:00 2001
From: Phil Sutter <psutter@redhat.com>
Date: Tue, 6 Mar 2018 11:35:28 +0100
Subject: [PATCH] ip-link: Fix use after free in nl_get_ll_addr_len()

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1550097
Upstream Status: iproute2.git commit 06867c3719587

commit 06867c371958773e39b4ccac07cfe3e2fff2ea55
Author: Phil Sutter <phil@nwl.cc>
Date:   Thu Mar 1 10:35:12 2018 +0100

    ip-link: Fix use after free in nl_get_ll_addr_len()

    Immediately after freeing the buffer returned from rtnl_talk(), it is
    accessed again via pointer in struct rtattr array. This leads to some
    builds not allowing to set an interface's MAC address because the
    expected length value is garbage.

    Fixes: 86bf43c7c2fdc ("lib/libnetlink: update rtnl_talk to support malloc buff at run time")
    Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 ip/iplink.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ip/iplink.c b/ip/iplink.c
index 193997c..db5b2c9 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -268,8 +268,9 @@ static int nl_get_ll_addr_len(unsigned int dev_index)
 		return -1;
 	}
 
+	len = RTA_PAYLOAD(tb[IFLA_ADDRESS]);
 	free(answer);
-	return RTA_PAYLOAD(tb[IFLA_ADDRESS]);
+	return len;
 }
 
 static void iplink_parse_vf_vlan_info(int vf, int *argcp, char ***argvp,
-- 
1.8.3.1