From fc9fdbcc09f214c6e0ea4a2b5bf61aa28e6082ef Mon Sep 17 00:00:00 2001
From: Rion Bora <223810819+GoldenEmperor1177@users.noreply.github.com>
Date: Mon, 12 Oct 2026 12:18:38 +0530
Subject: [PATCH] MDEV-40545 mariadb-binlog --force-read loops on truncated
 events

What was wrong:
With --force-read, Log_event::read_log_event() returned a synthetic
"Encrypted event" (Unknown_log_event) for every read error. A
truncated event is such an error, so mariadb-binlog printed a fake
event instead of stopping, and on most truncated binlogs it then never
stopped at all.

How it is fixed:
The synthetic event is meant for encrypted events that mariadb-binlog
cannot decrypt (MDEV-11319). It is now returned only for a decryption
failure. Other read errors, like a truncated event or an out of memory
error, are critical: continuing after them cannot produce meaningful
output, so they are reported and mariadb-binlog stops as it does
without --force-read.

How it is tested:
main.mysqlbinlog_force_read_truncated reads two truncated binlogs from
std_data, one with a truncated event header and one with a truncated
event body. The test loops forever without the fix.
---
 .../mysqlbinlog_force_read_truncated.result   |  18 ++++++++++++++++++
 .../mysqlbinlog_force_read_truncated.test     |  13 +++++++++++++
 .../std_data/truncated_binlog_body.000001     | Bin 0 -> 50 bytes
 .../std_data/truncated_binlog_header.000001   | Bin 0 -> 17 bytes
 sql/log_event.cc                              |   9 ++++-----
 5 files changed, 35 insertions(+), 5 deletions(-)
 create mode 100644 mysql-test/main/mysqlbinlog_force_read_truncated.result
 create mode 100644 mysql-test/main/mysqlbinlog_force_read_truncated.test
 create mode 100644 mysql-test/std_data/truncated_binlog_body.000001
 create mode 100644 mysql-test/std_data/truncated_binlog_header.000001

diff --git a/mysql-test/main/mysqlbinlog_force_read_truncated.result b/mysql-test/main/mysqlbinlog_force_read_truncated.result
new file mode 100644
index 00000000000..c61b2d1dc26
--- /dev/null
+++ b/mysql-test/main/mysqlbinlog_force_read_truncated.result
@@ -0,0 +1,18 @@
+#
+# MDEV-40545: --force-read must not loop on a truncated event
+#
+# The event header is truncated
+/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
+/*!40019 SET @@session.max_delayed_threads=0*/;
+/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
+DELIMITER /*!*/;
+ERROR: Error in Log_event::read_log_event(): 'Event truncated'
+ERROR: Could not read entry at offset 4: Error in log format or read error.
+# The event body is truncated
+/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
+/*!40019 SET @@session.max_delayed_threads=0*/;
+/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
+DELIMITER /*!*/;
+ERROR: Error in Log_event::read_log_event(): 'Event truncated', data_len: 94, event_type: 15
+ERROR: Could not read entry at offset 4: Error in log format or read error.
+# End of 11.4 tests
diff --git a/mysql-test/main/mysqlbinlog_force_read_truncated.test b/mysql-test/main/mysqlbinlog_force_read_truncated.test
new file mode 100644
index 00000000000..dde1747ac87
--- /dev/null
+++ b/mysql-test/main/mysqlbinlog_force_read_truncated.test
@@ -0,0 +1,13 @@
+--echo #
+--echo # MDEV-40545: --force-read must not loop on a truncated event
+--echo #
+
+--echo # The event header is truncated
+--error 1
+--exec $MYSQL_BINLOG --short-form --force-read $MYSQL_TEST_DIR/std_data/truncated_binlog_header.000001 2>&1
+
+--echo # The event body is truncated
+--error 1
+--exec $MYSQL_BINLOG --short-form --force-read $MYSQL_TEST_DIR/std_data/truncated_binlog_body.000001 2>&1
+
+--echo # End of 11.4 tests
diff --git a/mysql-test/std_data/truncated_binlog_body.000001 b/mysql-test/std_data/truncated_binlog_body.000001
new file mode 100644
index 0000000000000000000000000000000000000000..ba231a91034f22ae231f3801d9ba0c706d5f172f
GIT binary patch
literal 50
xcmeyDl$rO(bhj5jBLf3N91te~F#`h&gQ=c@o`soiN@`MRx^7N>I#?J)0028x3KReU

literal 0
HcmV?d00001

diff --git a/mysql-test/std_data/truncated_binlog_header.000001 b/mysql-test/std_data/truncated_binlog_header.000001
new file mode 100644
index 0000000000000000000000000000000000000000..c0917e96d8b32f2889f1355ddb358f5ef2b22603
GIT binary patch
literal 17
WcmeyDl$poK#LU9X$N&Vq3=9Ax@&Z!;

literal 0
HcmV?d00001

diff --git a/sql/log_event.cc b/sql/log_event.cc
index 9e01ee66bc4..5cfd2818083 100644
--- a/sql/log_event.cc
+++ b/sql/log_event.cc
@@ -935,6 +935,10 @@ Log_event* Log_event::read_log_event(IO_CACHE* file, int *out_error,
       error= "Event too big";
       goto err;
     case LOG_READ_DECRYPT:
+#ifdef MYSQL_CLIENT
+      if (force_opt)
+        DBUG_RETURN(new Unknown_log_event());
+#endif
       error= "Event decryption failure";
       goto err;
     case LOG_READ_CHECKSUM_FAILURE:
@@ -956,11 +960,6 @@ err:
   if (unlikely(error))
   {
     DBUG_ASSERT(!res);
-#ifdef MYSQL_CLIENT
-    if (force_opt)
-      DBUG_RETURN(new Unknown_log_event());
-#endif
-
     /*
       The SQL slave thread will check *out_error to know
       if there was an I/O error. Even if there is no "low-level" I/O errors