Created attachment 770465 [details]
full backtrace during the crash

The respective code from ping6.c:

struct addrinfo hints, *ai;
int gai;
...
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_INET6;
hints.ai_flags = AI_IDN;
gai = getaddrinfo(target, NULL, &hints, &ai); // <--- crash here
if (gai) {
	fprintf(stderr, "unknown host\n");
	exit(2);
}

Switching to glibc.

(gdb) bt
#0  0x00007ff8cc255895 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x00007ff8cc257075 in abort () at abort.c:92
#2  0x00007ff8cc2937a7 in __libc_message (do_abort=2, fmt=0x7ff8cc37af80 "*** glibc detected *** %s: %s: 0x%s ***\n")
    at ../sysdeps/unix/sysv/linux/libc_fatal.c:198
#3  0x00007ff8cc2990d6 in malloc_printerr (action=3, str=0x7ff8cc37afb0 "munmap_chunk(): invalid pointer", 
    ptr=<value optimized out>) at malloc.c:6311
#4  0x00007ff8cc2f3252 in gaih_inet (
    name=0x7fff88db2536 "தளம்.பாராளுமன்றம்.இலங்கை.", 
    service=<value optimized out>, req=<value optimized out>, pai=<value optimized out>, naddrs=0x7fff88db1d48)
    at ../sysdeps/posix/getaddrinfo.c:1250
#5  0x00007ff8cc2f5da0 in getaddrinfo (
    name=0x7fff88db2536 "தளம்.பாராளுமன்றம்.இலங்கை.", 
    service=<value optimized out>, hints=0x7fff88db1dc0, pai=0x7fff88db1e18) at ../sysdeps/posix/getaddrinfo.c:2361
#6  0x00007ff8cc7db2f5 in main ()


The problem is like this:

* In gaih_inet we pass this IDN to __idna_to_ascii_lz to get back a canonicalized name we can use.
* If the output string of __idna_to_ascii_lz (second argument) has a different pointer value from the IDN then we assume a string has been allocated that we need to free.
* Later we free name (the static string).

The disconnect is that we did not assign `name' to the new value `p' which needs to be freed.

The upstream code is this:
~~~
          /* In case the output string is the same as the input string
             no new string has been allocated.  */
          if (p != name)
            {
              name = p;
              malloc_name = true;
            }
~~~

The rhel-6.5 code is this:
~~~
 432           /* In case the output string is the same as the input string
 433              no new string has been allocated.  */
 434           if (p != name)
 435             malloc_name = true;
~~~

The upstream fix is this:

commit 2e96f1c73b06e81da59ef7fffa426dc201875f31
Author: Andreas Schwab <schwab>
Date:   Thu Aug 4 15:42:10 2011 -0400

    Fix encoding name for IDN in getaddrinfo

~~~
diff --git a/ChangeLog b/ChangeLog
index fbacbd5..0392853 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2011-07-26  Andreas Schwab  <schwab>
+
+       * sysdeps/posix/getaddrinfo.c (gaih_inet): Don't discard result of
+       encoding to ACE if AI_IDN.
+
 2011-08-01  Jakub Jelinek  <jakub>
 
        * sysdeps/ieee754/dbl-64/k_rem_pio2.c (__kernel_rem_pio2): Fix up fq
diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 6d574c5..a5aafe9 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -432,7 +432,10 @@ gaih_inet (const char *name, const struct gaih_service *service,
          /* In case the output string is the same as the input string
             no new string has been allocated.  */
          if (p != name)
-           malloc_name = true;
+           {
+             name = p;
+             malloc_name = true;
+           }
        }
 #endif
~~~

According to http://sourceware.org/glibc/wiki/Glibc%20Timeline, that fixed happened in the 2.15 development cycle which would not have been in rhel-6.5 which uses 2.12.

This fix needs backporting to correct this issue.

Moving to rhel-6.6.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2014-1391.html