race condition in referrals fallback

race condition in referrals fallback

	* src/lib/krb5/krb/gc_frm_kdc.c (krb5_get_cred_from_kdc_opt):
	During referrals fallback, set *tgts to NULL after freeing.  This
	avoids returning a pointer to freed memory when the first call to
	do_traversal() obtains some TGTs and the subsequent
	krb5_cc_retrieve_cred() of the final-hop TGT succeeds (due to some
	other thread or process storing that TGT into the ccache), causing
	second do_traversal() call (which would re-initialize *tgts) to
	not execute.  Race condition found during KfW-3.2 testing.

ticket: new
target_version: 1.6.2
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@19526 dc483132-0cff-0310-8789-dd5450dbe970