From: Nicolas Williams <nico@cryptonector.com>
Date: Wed, 12 Sep 2012 16:36:54 +0000 (-0500)
Subject: Fix lock inconsistency in ctx_unlock()
X-Git-Tag: krb5-1.11-alpha1~180
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=29ee39baa919361ae08e26caab896890d5cb3eb4;p=thirdparty%2Fkrb5.git

Fix lock inconsistency in ctx_unlock()

The lock inconsistency fixed here is quite possibly the same as
described in https://bugzilla.redhat.com/show_bug.cgi?id=586032 .

The problem is that ctx_unlock() fails to unlock the principal DB if
it fails to unlock the policy DB, and this happens when ctx_lock()
fails to lock the policy DB (likely because the caller is racing
against a kdb5_util load, which will be using a "permanent" lock,
meaning that the lock file will be unlinked after acquiring the
lock).  The fix is to perform both unlock operations *then* handle
any errors that either or both might have returned.

Additionally, we don't really need or want to use non-blocking locks,
and we certainly don't want to sleep(1) in krb5kdc (possibly several
times, as there was a loop over this) when either of the principal or
policy DB is locked.  Some callers still request non-blocking locks,
and ctx_lock() still honors this.

ticket: 7360 (new)
---

diff --git a/src/plugins/kdb/db2/kdb_db2.c b/src/plugins/kdb/db2/kdb_db2.c
index 87b6c182b8..62fbef748b 100644
--- a/src/plugins/kdb/db2/kdb_db2.c
+++ b/src/plugins/kdb/db2/kdb_db2.c
@@ -383,12 +383,10 @@ done:
 static krb5_error_code
 ctx_unlock(krb5_context context, krb5_db2_context *dbc)
 {
-    krb5_error_code retval;
+    krb5_error_code retval, retval2;
     DB *db;
 
     retval = osa_adb_release_lock(dbc->policy_db);
-    if (retval)
-        return retval;
 
     if (!dbc->db_locks_held) /* lock already unlocked */
         return KRB5_KDB_NOTLOCKED;
@@ -399,9 +397,15 @@ ctx_unlock(krb5_context context, krb5_db2_context *dbc)
         dbc->db = NULL;
         dbc->db_lock_mode = 0;
 
-        retval = krb5_lock_file(context, dbc->db_lf_file,
+        retval2 = krb5_lock_file(context, dbc->db_lf_file,
                                 KRB5_LOCKMODE_UNLOCK);
+        if (retval2)
+            return retval2;
     }
+
+    /* We may be unlocking because osa_adb_get_lock() failed. */
+    if (retval == OSA_ADB_NOTLOCKED)
+        return 0;
     return retval;
 }