On (07/04/14 18:53), Jakub Hrozek wrote:
>On Fri, Apr 04, 2014 at 03:41:38PM +0200, Lukas Slebodnik wrote:
>> On (04/04/14 15:18), Jakub Hrozek wrote:
>> >On Thu, Apr 03, 2014 at 07:11:37PM +0200, Jakub Hrozek wrote:
>> >> On Thu, Mar 20, 2014 at 05:53:31PM +0100, Lukas Slebodnik wrote:
>> >> > On (20/03/14 17:21), Jakub Hrozek wrote:
>> >> > >On Thu, Mar 20, 2014 at 05:00:00PM +0100, Sumit Bose wrote:
>> >> > >> On Thu, Mar 20, 2014 at 04:20:59PM +0100, Lukas Slebodnik wrote:
>> >> > >> > ehlo,
>> >> > >> >
>> >> > >> > debug_prg_name is used in debug_fn and it was allocated under
>> >> > >> > talloc context "kr". The variable "kr" was removed before the last
>> >> > >> > debug
>> >> > >> > messages in function main. It is very little change that it will
>> >> > >> > be overridden.
>> >> > >> >
>> >> > >> > It is possible to see this issue with exported environment variable
>> >> > >> > TALLOC_FREE_FILL=255
>> >> > >>
>> >> > >> I'm pretty sure the patch works as expected and fixes the isssue.
>> >> > >> But I
>> >> > >> wonder if a different approach might be better? I think it does not
>> >> > >> make
>> >> > >> sense to allocate debug_prg_name on a given talloc context but that
>> >> > >> it
>> >> > >> would be better to just allocate it on NULL. This is e.g. done in the
>> >> > >> ldap_child (here a talloc_free() is missing on exit but this would
>> >> > >> be a
>> >> > >> different story). Then debug_prg_name can even be allocate before kr
>> >> > >> and the debug messages for a failed allocation of kr can use the
>> >> > >> right
>> >> > >> program name and not "sssd".
>> >> > >
>> >> > >I agree, because also given that krb5_child is a short lived process,
>> >> > >we don't care too much about possible leaks.
>> >> > No problem.
>> >> >
>> >> > New version attached.
>> >> >
>> >> > LS
>> >>
>> >> This version works for me, do you want to also add a talloc_free() on
>> >> exit to be clean or do you also consider this not needed for short-lived
>> >> processes?
>> >
>> >Thinking again, it would be nicer to explicitly free the string on child
>> >exit. Yes, the leak it's not a big deal for a short-lived process but it
>> >would read better.
>>
>> With the first version of patch string was freed, because it was alocated
>> under "kr" context.
>> Now, you should decide which version do you want to push :-)
>>
>> LS
>
>I think it's easier to explain with a patch :-)
You didn't test your patch :-)
diff --git a/src/providers/krb5/krb5_child.c b/src/providers/krb5/krb5_child.c
index
764f6ac7bf57b1f7d882961b7c6fa518818aaf23..aec0d9389dd4f3ae005b73ff12ca8293cee7560f
100644
--- a/src/providers/krb5/krb5_child.c
+++ b/src/providers/krb5/krb5_child.c
@@ -2013,6 +2013,7 @@ int main(int argc, const char *argv[])
DEBUG(SSSDBG_CRIT_FAILURE, "talloc failed.\n");
exit(-1);
}
+ talloc_steal(kr, debug_prg_name);
if (debug_fd != -1) {
ret = set_debug_file_from_fd(debug_fd);
// snip
done:
krb5_cleanup(kr);
talloc_free(kr);
^^^^^^^^^^^^^^^
//debug_prg_name is freed
if (ret == EOK) {
DEBUG(SSSDBG_TRACE_FUNC, "krb5_child completed successfully\n");
^^^^^^
// use after free
exit(0);
} else {
DEBUG(SSSDBG_CRIT_FAILURE, "krb5_child failed!\n");
^^^^^^
// use after free
exit(-1);
}
LS
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