pgpool2.git / summary / log / commit / refs

commit    226afe2f0efb70d6ce986d5f4d97da2f369f69b1
Author:   Tatsuo Ishii <ishii@sraoss.co.jp>
Date:     Thu Jan 10 03:20:07 2019 +0000

    Fix Pgpool child segfault in a race condition.
    
    1) frontend tries to connect to Pgpool-II
    
    2) there's no existing connection cache
    
    3) try to create new backend connections by calling connect_backend()
    
    4) inside connect_backend(), pool_create_cp() gets called
    
    5) pool_create_cp() calls new_connection()
    
    6) failover occurs and the global backend status is set to down, but
       the pgpool main does not send kill signal to the child process yet
    
    7) inside new_connection() after checking VALID_BACKEND, it checks the
       global backend status and finds it is set to down status, so that
       it returns without creating new connection slot
    
    8) connect_backend() continues and accesses the down connection slot
       because local status says it's alive, which results in a segfault.
    
    Since there's already checking for the global status in
    new_connection(), a fix could be syncing the local status with the
    global status there.
    
    See [pgpool-hackers: 3214] for discussion.


 src/protocol/pool_connection_pool.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/protocol/pool_connection_pool.c b/src/protocol/pool_connection_pool.c
index 6370cb5f8..80d106a15 100644
--- a/src/protocol/pool_connection_pool.c
+++ b/src/protocol/pool_connection_pool.c
@@ -5,7 +5,7 @@
  * pgpool: a language independent connection pool server for PostgreSQL
  * written by Tatsuo Ishii
  *
- * Copyright (c) 2003-2015	PgPool Global Development Group
+ * Copyright (c) 2003-2019	PgPool Global Development Group
  *
  * Permission to use, copy, modify, and distribute this software and
  * its documentation for any purpose and without fee is hereby
@@ -882,6 +882,9 @@ static POOL_CONNECTION_POOL * new_connection(POOL_CONNECTION_POOL * p)
 					(errmsg("creating new connection to backend"),
 					 errdetail("skipping backend slot %d because global backend_status = %d",
 							   i, BACKEND_INFO(i).backend_status)));
+
+			/* sync local status with global status */
+			*(my_backend_status[i]) = BACKEND_INFO(i).backend_status;
 			continue;
 		}
 
@@ -915,7 +918,7 @@ static POOL_CONNECTION_POOL * new_connection(POOL_CONNECTION_POOL * p)
 					/* set down status to local status area */
 					*(my_backend_status[i]) = CON_DOWN;
 
-					/* if master_node_id is not updated, the update it */
+					/* if master_node_id is not updated, then update it */
 					if (Req_info->master_node_id == i)
 					{
 						int			old_master = Req_info->master_node_id;


[parent: 93ff97e0b8fe]