CVE: CVE-2018-19591
Upstream-Status: Backport
Signed-off-by: Ross Burton <ross.burton@intel.com>

From ce6ba630dbc96f49eb1f30366aa62261df4792f9 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Tue, 27 Nov 2018 16:12:43 +0100
Subject: [PATCH] CVE-2018-19591: if_nametoindex: Fix descriptor for overlong
 name [BZ #23927]

(cherry picked from commit d527c860f5a3f0ed687bd03f0cb464612dc23408)
---
 ChangeLog                          |  7 +++++++
 NEWS                               |  6 ++++++
 sysdeps/unix/sysv/linux/if_index.c | 11 ++++++-----
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/if_index.c b/sysdeps/unix/sysv/linux/if_index.c
index e3d08982d9..782fc5e175 100644
--- a/sysdeps/unix/sysv/linux/if_index.c
+++ b/sysdeps/unix/sysv/linux/if_index.c
@@ -38,11 +38,6 @@ __if_nametoindex (const char *ifname)
   return 0;
 #else
   struct ifreq ifr;
-  int fd = __opensock ();
-
-  if (fd < 0)
-    return 0;
-
   if (strlen (ifname) >= IFNAMSIZ)
     {
       __set_errno (ENODEV);
@@ -50,6 +45,12 @@ __if_nametoindex (const char *ifname)
     }
 
   strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
+
+  int fd = __opensock ();
+
+  if (fd < 0)
+    return 0;
+
   if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
     {
       int saved_errno = errno;
-- 
2.11.0