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

[Florian Weimer]

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
> it.
> 
> Jason
> 
> 
> --- 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 <sellcey@caviumnetworks.com>
Date:   Wed Nov 15 08:58:48 2017 -0800

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

Thanks,
Florian