Fix syslogger NULL-pointer-dereference in EXEC_BACKEND

Commit 0c8e082fba8d changed the time at which MyBackendType is assigned,
breaking a careful choreography in syslogger to decide when to write
messages to its own log files.  Fix by flipping a boolean at the
(approximate) location where previously MyBackendType was set, instead
of depending on MyBackendType directly.

Author: Álvaro Herrera <alvherre@kurilemu.de>
Reported-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Euler Taveira <euler@eulerto.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/ahP-JT4ZRPyobnLb@paquier.xyz

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index acfe0a01715e642d5b3b06aed3d5068840618bc9..7645c495a815c686145ae76e4d41657eb5a85ea5 100644 (file)
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -76,6 +76,12 @@ char    *Log_filename = NULL;
 bool           Log_truncate_on_rotation = false;
 int                    Log_file_mode = S_IRUSR | S_IWUSR;
 
+/*
+ * Indicates to be running in the syslogger process, and that the logging
+ * file descriptor(s) have been set up.
+ */
+bool           syslogger_setup_done = false;
+
 /*
  * Private state
  */
@@ -175,6 +181,17 @@ SysLoggerMain(const void *startup_data, size_t startup_data_len)
        pg_time_t       now;
        WaitEventSet *wes;
 
+#ifndef EXEC_BACKEND
+
+       /*
+        * In !EXEC_BACKEND, syslogger is immediately ready to take over: the
+        * output files were already opened by postmaster before forking.  For the
+        * other case we must wait until the file descriptors have been restored,
+        * below.
+        */
+       syslogger_setup_done = true;
+#endif
+
        /*
         * Re-open the error output files that were opened by SysLogger_Start().
         *
@@ -190,6 +207,8 @@ SysLoggerMain(const void *startup_data, size_t startup_data_len)
                syslogFile = syslogger_fdopen(slsdata->syslogFile);
                csvlogFile = syslogger_fdopen(slsdata->csvlogFile);
                jsonlogFile = syslogger_fdopen(slsdata->jsonlogFile);
+
+               syslogger_setup_done = true;
        }
 #else
        Assert(startup_data_len == 0);

diff --git a/src/backend/utils/error/csvlog.c b/src/backend/utils/error/csvlog.c
index 2b2b9484bdcbd1767a5e24480ac405edfbd8f14f..ee4e2a7104a635b3be13017a53c4aba8a48372ea 100644 (file)
--- a/src/backend/utils/error/csvlog.c
+++ b/src/backend/utils/error/csvlog.c
@@ -253,7 +253,7 @@ write_csvlog(ErrorData *edata)
        appendStringInfoChar(&buf, '\n');
 
        /* If in the syslogger process, try to write messages direct to file */
-       if (MyBackendType == B_LOGGER)
+       if (syslogger_setup_done)
                write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
        else
                write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 50c53b571a049b95222633980c1a8c54cfde7539..a6936a0c664a9895acc49176438450217769781a 100644 (file)
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -3831,7 +3831,7 @@ send_message_to_server_log(ErrorData *edata)
                 * pipe).  If this is not possible, fallback to an entry written to
                 * stderr.
                 */
-               if (redirection_done || MyBackendType == B_LOGGER)
+               if (redirection_done || syslogger_setup_done)
                        write_csvlog(edata);
                else
                        fallback_to_stderr = true;
@@ -3845,7 +3845,7 @@ send_message_to_server_log(ErrorData *edata)
                 * pipe).  If this is not possible, fallback to an entry written to
                 * stderr.
                 */
-               if (redirection_done || MyBackendType == B_LOGGER)
+               if (redirection_done || syslogger_setup_done)
                {
                        write_jsonlog(edata);
                }
@@ -3885,7 +3885,7 @@ send_message_to_server_log(ErrorData *edata)
        }
 
        /* If in the syslogger process, try to write messages direct to file */
-       if (MyBackendType == B_LOGGER)
+       if (syslogger_setup_done)
                write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_STDERR);
 
        /* No more need of the message formatted for stderr */

diff --git a/src/backend/utils/error/jsonlog.c b/src/backend/utils/error/jsonlog.c
index e5ba22794d2555de5d611aa43ec2194ccc58b8be..4a76072830dc3226a54d2d5b49c8691110d6a1f8 100644 (file)
--- a/src/backend/utils/error/jsonlog.c
+++ b/src/backend/utils/error/jsonlog.c
@@ -292,7 +292,7 @@ write_jsonlog(ErrorData *edata)
        appendStringInfoChar(&buf, '\n');
 
        /* If in the syslogger process, try to write messages direct to file */
-       if (MyBackendType == B_LOGGER)
+       if (syslogger_setup_done)
                write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_JSONLOG);
        else
                write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_JSONLOG);

diff --git a/src/include/postmaster/syslogger.h b/src/include/postmaster/syslogger.h
index 30c4b2daf3f660d98b82e1d80916ffabeec6c973..44409fc2542d5e9d9a940fbc7c2401e639f2311b 100644 (file)
--- a/src/include/postmaster/syslogger.h
+++ b/src/include/postmaster/syslogger.h
@@ -85,6 +85,7 @@ extern PGDLLIMPORT int syslogPipe[2];
 extern PGDLLIMPORT HANDLE syslogPipe[2];
 #endif
 
+extern bool syslogger_setup_done;
 
 extern int     SysLogger_Start(int child_slot);