Segfaults in MIT libkrb5

[Fredrik Tolf]

Hi list!

I'm experiencing weird segfaults in a program I've written. While I
cannot exactly prove that it isn't my own fault and I'm not just doing a
great fandango all over libkrb5's core, they all occur in the Kerberos
library, in incidents seemingly related to the error tables. The usual
backtrace looks like this:

#0  0xb7d52a43 in error_message (code=-1429577725) at error_message.c:58
#1  0xb7f0e598 in krb5int_locate_server () from /usr/lib/libkrb5.so.3
#2  0xb7f0e843 in krb5_locate_kdc () from /usr/lib/libkrb5.so.3
#3  0xb7f1072f in krb5_sendto_kdc () from /usr/lib/libkrb5.so.3
#4  0xb7eff3e0 in krb5_send_tgs () from /usr/lib/libkrb5.so.3
#5  0xb7ef0b6d in krb5_get_cred_via_tkt () from /usr/lib/libkrb5.so.3
#6  0xb7eeff0e in krb5_fwd_tgt_creds () from /usr/lib/libkrb5.so.3
#7  0xb7ef183d in krb5_get_credentials_renew ()
from /usr/lib/libkrb5.so.3
#8  0x08061df1 in renewcreds (cancelled=0, data=0x835bd18) at
auth-krb5.c:228
#9  0x0804c9a0 in main (argc=1, argv=0xbfac4104) at main.c:550

Today, however, I got another segfault, but which also seems related to
the error tables:
#0  0xb7a2ff63 in krb_realmofhost () from /usr/lib/libkrb4.so.2
#1  0xb7a2ffd0 in initialize_krb_error_table ()
from /usr/lib/libkrb4.so.2
#2  0xb7ba21c1 in _pam_krb5_init_ctx (ctx=0x8443e88, argc=2,
argv=0x8422530) at init.c:80
...

Could the fault somehow be related to the fact that this particular
program both uses the Kerberos library directly (for Kerberized clients)
and the pam_krb5 PAM module (which is line #2 in the second backtrace
above), which is called from a userspace thread (using the ucontext
calls)? Is there some other known problem? I also call the seemingly
undocumented function krb5_get_credentials_renew, if that might matter.

I'm using MIT Kerberos V 1.4.3 and a system-supplied com_err library,
version 1.39. The system is Gentoo Linux.

For reference, the program in question is the daemon in Dolda Connect,
at <http://www.dolda2000.com/~fredrik/doldaconnect/>

I would be very glad for any assistance!

Fredrik Tolf