[trafficserver] branch 9.0.x updated: Fix code to avoid HostDBContinuation use after free

[zw...@apache.org]

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zwoop pushed a commit to branch 9.0.x
in repository https://gitbox.apache.org/repos/asf/trafficserver.git


The following commit(s) were added to refs/heads/9.0.x by this push:
     new 153c081  Fix code to avoid HostDBContinuation use after free
153c081 is described below

commit 153c08166ed3ba83f92064e607b37210fa34c297
Author: Susan Hinrichs <sh...@oath.com>
AuthorDate: Fri Sep 20 18:00:28 2019 +0000

    Fix code to avoid HostDBContinuation use after free
    
    (cherry picked from commit f27f90dd0f1eb38b5c4e2094f1710536d9a32682)
---
 iocore/hostdb/HostDB.cc | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/iocore/hostdb/HostDB.cc b/iocore/hostdb/HostDB.cc
index 512781f..2ee0e22 100644
--- a/iocore/hostdb/HostDB.cc
+++ b/iocore/hostdb/HostDB.cc
@@ -1178,8 +1178,9 @@ HostDBContinuation::dnsEvent(int event, HostEnt *e)
   if (event == EVENT_INTERVAL) {
     if (!action.continuation) {
       // give up on insert, it has been too long
+      // remove_trigger_pending_dns will notify and clean up all requests
+      // including this one.
       remove_trigger_pending_dns();
-      hostdb_cont_free(this);
       return EVENT_DONE;
     }
     MUTEX_TRY_LOCK(lock, action.mutex, thread);
@@ -1434,18 +1435,18 @@ HostDBContinuation::dnsEvent(int event, HostEnt *e)
         }
       }
       if (need_to_reschedule) {
-        remove_trigger_pending_dns();
         SET_HANDLER((HostDBContHandler)&HostDBContinuation::probeEvent);
-        thread->schedule_in(this, HOST_DB_RETRY_PERIOD);
+        // remove_trigger_pending_dns should kick off the current hostDB too
+        // No need to explicitly reschedule
+        remove_trigger_pending_dns();
         return EVENT_CONT;
       }
     }
     // wake up everyone else who is waiting
     remove_trigger_pending_dns();
 
-    // all done
+    // all done, or at least scheduled to be all done
     //
-    hostdb_cont_free(this);
     return EVENT_DONE;
   }
 }