[18876] in Kerberos_V5_Development
Re: krb5_free_data
daemon@ATHENA.MIT.EDU (Markus Moeller)
Sat Jun 21 19:28:36 2014
Message-ID: <A49DE66FB81A426ABF40AC8FD08C3F50@Ultrabook1>
From: "Markus Moeller" <huaraz@moeller.plus.com>
To: "Greg Hudson" <ghudson@mit.edu>, <krbdev@mit.edu>
In-Reply-To: <53A608E5.7090800@mit.edu>
Date: Sun, 22 Jun 2014 00:28:18 +0100
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Errors-To: krbdev-bounces@mit.edu
Hi Greg,
I see this in krb5 1.8.3
(gdb) where
#0 0x00007ffff5f911b5 in *__GI_raise (sig=<value optimized out>) at
../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1 0x00007ffff5f93fc0 in *__GI_abort () at abort.c:92
#2 0x00007ffff5fc75bb in __libc_message (do_abort=<value optimized out>,
fmt=<value optimized out>) at ../sysdeps/unix/sysv/linux/libc_fatal.c:189
#3 0x00007ffff5fd0e16 in malloc_printerr (action=3, str=0x7ffff6088748
"double free or corruption (fasttop)", ptr=<value optimized out>)
at malloc.c:6267
#4 0x00007ffff5fd5b8c in *__GI___libc_free (mem=<value optimized out>) at
malloc.c:3739
#5 0x00007ffff7939472 in krb5_free_data (context=<value optimized out>,
val=0x6171f0) at ../../../../src/lib/krb5/krb/kfree.c:253
#6 0x00000000004051a4 in get_ad_groups (ad_groups=0x7fffffffaff0 "",
context=0x60f9e0, pac=0x0) at negotiate_kerberos_pac.cc:464
#7 0x0000000000403265 in main (argc=5, argv=0x7fffffffe0e8) at
negotiate_kerberos_auth.cc:419
and line 253 is free(val->data)
The code I have is the following and I get an error in krb5_pac_get_buffer:
Invalid argument
ad_data = (krb5_data *)xmalloc(sizeof(krb5_data));
#define KERB_LOGON_INFO 1
ret = krb5_pac_get_buffer(context, pac, KERB_LOGON_INFO, ad_data);
if (check_k5_err(context, "krb5_pac_get_buffer", ret))
goto k5clean;
k5clean:
krb5_free_data(context, ad_data);
Maybe there is something wrong. I usually do not get this error, but I don't
know why it happens sometimes.
Markus
-----Original Message-----
From: Greg Hudson
Sent: Saturday, June 21, 2014 11:36 PM
To: Markus Moeller ; krbdev@mit.edu
Subject: Re: krb5_free_data
On 06/21/2014 05:17 PM, Markus Moeller wrote:
> Sorry I do not understand. Right now I get crashes as val->data is NULL.
free(NULL) does not crash. See section 7.20.3.2 of:
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf
or:
http://pubs.opengroup.org/onlinepubs/009695399/functions/free.html
We make this assumption all over the krb5 code base, as do many other
programs. Perhaps the crashes you are seeing have another cause?
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