Fix elog.c to avoid infinite recursion (leading to backend crash) when

log_min_error_statement is active and there is some problem in logging the
current query string; for example, that it's too long to include in the log
message without running out of memory.  This problem has existed since the
log_min_error_statement feature was introduced.  No doubt the reason it
wasn't detected long ago is that 8.2 is the first release that defaults
log_min_error_statement to less than PANIC level.
Per report from Bill Moran.

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index b0db9a685b538414eeb42ab5d719f338dba63253..6c22d57a85171576515f92eb14ffa1df50cf6782 100644 (file)
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -429,13 +429,18 @@ elog(int lev, const char *fmt,...)
                free(msg_buf);
 
        /*
-        * If the user wants this elog() generating query logged, do so. We
-        * only want to log if the query has been written to
-        * debug_query_string. Also, avoid infinite loops.
+        * If the user wants this elog() generating query logged, do so.
+        * To avoid possible infinite recursion, temporarily clear
+        * debug_query_string while recursing.
         */
+       if (lev >= log_min_error_statement && debug_query_string)
+       {
+               char   *q_str = debug_query_string;
 
-       if (lev != LOG && lev >= log_min_error_statement && debug_query_string)
-               elog(LOG, "statement: %s", debug_query_string);
+               debug_query_string = NULL;
+               elog(LOG, "statement: %s", q_str);
+               debug_query_string = q_str;
+       }
 
        /*
         * Perform error recovery action as specified by lev.