[PATCH] add attribute nonstring

[Steve Ellcey]

On Sun, 2017-11-12 at 16:49 -0700, Martin Sebor wrote:
> 
> PS I still don't see it discussed on the Linux man page but
> I did find such a requirement on an AIX 6.1 ioctl man page:
> https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_61/apis/ioct
> l.htm
> 
> The descriptions of the if_indextoname and if_nametoindex
> functions specified by RFC 3493 also talk about the name being
> a nul-terminated string so it looks to me like you are correct
> and the warning has found a Glibc bug.  Yay! :)

I think this is a bug and that if_nametoindex should check for a name
that is too long. Â Based on RFC 3493 it would appear that we don't need
to set errno in this case though I am not sure if that is a correct
interpretation. Â I tested this patch:


2017-11-13  Steve Ellcey  <sellcey@cavium.com>

	* sysdeps/unix/sysv/linux/if_index.c (__if_nametoindex):
	Check if ifname is too long.


diff --git a/sysdeps/unix/sysv/linux/if_index.c
b/sysdeps/unix/sysv/linux/if_index.c
index 56f3f13..1e081c0 100644
--- a/sysdeps/unix/sysv/linux/if_index.c
+++ b/sysdeps/unix/sysv/linux/if_index.c
@@ -43,6 +43,9 @@ __if_nametoindex (const char *ifname)
   if (fd < 0)
     return 0;
 
+Â Â if (strlen (ifname) >= IFNAMSIZ)
+Â Â Â Â return 0;
+
   strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
   if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
     {


And it compiled fine using the latest GCC. Â Apparently GCC's constant
propogation allowed it to see that sizeof could not longer be IFNAMSIZ.

Steve Ellcey