[OpenAFS] Re: "unable to authenticate to AFS" error- linux distribution, specific?

[Christof Hanke]

Douglas E. Engert wrote:

> It could also mean that the stack was being overlayed, and moving this
> variabe to static means something else on the stack is being overlayed.
>
> Two other things to try:
>
>  Compile without optimizatrion.
>
>  Use the debugger s to set a watch point on the ans_label before calling
>  the ka_Authenticate. Hopefully the debugger will catch the location 
> where
>  it ws being modified.
>
You were right.
The gdb found it was modified in ubik/ubikclient.c: ubik_CallIter()
This function takes 20 parameters :
afs_int32
ubik_CallIter(aproc, aclient, aflags, apos, p1, p2, p3, p4, p5, p6, p7, p8,
              p9, p10, p11, p12, p13, p14, p15, p16)
In kauth/authclient.c:kawrap_ubik_Call() it is called with only 12 
parameters :
477 : code = ubik_CallIter(aproc, aclient, aflags, &count, p1, p2, p3, p4,
478 :                             p5, p6, p7, p8);

Which is not uncommon, a wee grep showed up all sorts of numbers of 
paramters with wich ubik_CallIter() is called.

The real trick is now in ubik_CallIter() itself :
changing
777: code = CallIter(aproc, aclient, aflags, apos, p1, p2, p3, p4, p5, 
p6, p7,
                    p8, p9, p10, p11, p12, p13, p14, p15, p16,NEED_LOCK);
to
777 :code = CallIter(aproc, aclient, aflags, apos, NEED_LOCK, p1, p2, 
p3, p4, p5, p6, p7,
778:                     p8, p9, p10, p11, p12, p13, p14, p15, p16);

and all following seems to fix the problem.
Here the patch :
 # diff ubikclient.c ubikclient_new.c
584,585c584,585
< CallIter(aproc, aclient, aflags, apos, p1, p2, p3, p4, p5, p6, p7, p8, p9,
<        p10, p11, p12, p13, p14, p15, p16, needlock)
---
 > CallIter(aproc, aclient, aflags, apos, needlock,p1, p2, p3, p4, p5, 
p6, p7, p8, p9,
 >        p10, p11, p12, p13, p14, p15, p16)
718,720c718,720
<               CallIter(aproc, aclient, aflags, &count, p1, p2, p3, p4, p5,
<                        p6, p7, p8, p9, p10, p11, p12, p13, p14, p15, p16,
<                        NO_LOCK);
---
 >               CallIter(aproc, aclient, aflags, &count, NO_LOCK,p1, 
p2, p3, p4, p5,
 >                        p6, p7, p8, p9, p10, p11, p12, p13, p14, p15, p16
 >                        );
776,777c776,777
<     return CallIter(aproc, aclient, aflags, apos, p1, p2, p3, p4, p5, 
p6, p7,
<                   p8, p9, p10, p11, p12, p13, p14, p15, p16, NEED_LOCK);
---
 >     return CallIter(aproc, aclient, aflags, apos, NEED_LOCK, p1, p2, 
p3, p4, p5,
 >                    p6,p7,p8, p9, p10, p11, p12, p13, p14, p15, p16);

Apparently, you cannot use a variable after the "optional ones", 
otherwise you corrupt the stack (?).

Then there is the question :
Wouldn't it be cleaner to call the function with the exact (real) number 
of parameters ?
I guess it would imply some performance penalties, but would they matter?

-Christof  Hanke