On Mon, Apr 07, 2014 at 08:39:07PM +0200, Jakub Hrozek wrote:
> On Mon, Apr 07, 2014 at 08:35:20PM +0200, Lukas Slebodnik wrote:
> > On (07/04/14 20:30), Jakub Hrozek wrote:
> > >On Mon, Apr 07, 2014 at 08:03:32PM +0200, Lukas Slebodnik wrote:
> > >> 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 :-)
> > >
> > >I left that to you :-)
> > >
> > >See another proposal below:
> > >
> > >>
> > >> 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
> > > talloc_free(tmp_str);
> > >> exit(0);
> > >> } else {
> > >> DEBUG(SSSDBG_CRIT_FAILURE, "krb5_child failed!\n");
> > >> ^^^^^^
> > >> // use after free
> > > talloc_free(tmp_str);
> > >> exit(-1);
> > >> }
> > >>
> > >
> > >Or just:
> > > done:
> > > krb5_cleanup(kr);
> > > talloc_free(kr);
> > > if (ret == EOK) {
> > > DEBUG(SSSDBG_TRACE_FUNC, "krb5_child completed successfully\n");
> > > talloc_free(tmp_str);
> > > rv = 0;
> > > } else {
> > > DEBUG(SSSDBG_CRIT_FAILURE, "krb5_child failed!\n");
> > > talloc_free(tmp_str);
> > > rv = -1;
> > > }
> > > exit(rv);
> >
> > And now, you can compare your solution with the first patch from this thread
> > and then try to read replies to the 1st mail from this thread :-)
>
> Except first patch didn't allocate on NULL? I think that was the meat of
> Sumit's comments..
yes, just allocate on NULL and free it explicitly in the end to make
valgrind happy. The reason for suggesting NULL is that debug_prg_name is
global and I think putting it under a specific talloc-hierarchy does not
make sense.
bye,
Sumit
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