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Re: [PATCH] fix strncpy overflow in sysdeps/unix/sysv/linux/if_index.c

On 02/20/2018 01:57 PM, Jason Duerstock wrote:
When compiling glibc with gcc-8, the strncpy() call in
__if_nametoindex() in sysdeps/unix/sysv/linux/if_index.c gets flagged
for a possible string overflow.  I believe the following patch fixes


--- sysdeps/unix/sysv/linux/if_index.c.orig     2018-02-20
07:35:09.835359401 -0500
+++ sysdeps/unix/sysv/linux/if_index.c  2018-02-20 07:51:45.919075043 -0500
@@ -43,7 +43,8 @@
    if (fd < 0)
      return 0;

-  strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
+  strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name) - 1);
+  ifr.ifr_name[strlen (ifname) - 1] = '\0';
    if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
        int saved_errno = errno;

Which sources are you looking at?

I believe this is bug 22442, and we fixed it in:

commit 2180fee114b778515b3f560e5ff1e795282e60b0
Author: Steve Ellcey <>
Date:   Wed Nov 15 08:58:48 2017 -0800

    Check length of ifname before copying it into to ifreq structure.


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