MDEV-38010: Fix trailing garbage in master.info causing data corruption

Modified init_intvar_from_file and init_floatvar_from_file to detect and reject trailing garbage in master.info numeric fields. Added a test case to verify the fix and ensure replication is correctly restored.

Author: ayush-jha123

mysql-test/main/mdev_38010.result

@@ -0,0 +1,16 @@
+include/master-slave.inc
+[connection master]
+connection slave;
+include/stop_slave.inc
+call mtr.add_suppression("Error reading master configuration");
+call mtr.add_suppression("Failed to initialize the master info structure");
+call mtr.add_suppression("error connecting to master");
+include/rpl_restart_server.inc [server_number=2]
+connection slave;
+# Verifying that trailing garbage causes parsing to fail.
+# Restoring the slave to original replication state
+include/rpl_restart_server.inc [server_number=2]
+CHANGE MASTER TO MASTER_HOST='MASTER_HOST', MASTER_PORT=MASTER_PORT, MASTER_USER='MASTER_USER';
+include/start_slave.inc
+connection master;
+include/rpl_end.inc

mysql-test/main/mdev_38010.test

@@ -0,0 +1,84 @@
+#
+# MDEV-38010: Trailing garbage in master.info numeric fields leads to corruption.
+# This test verifis that the server strictly validates numeric lines in master.info.
+# If trailing non-whitespace characters are found, the line is rejected as corrupted.
+#
+
+--source include/master-slave.inc
+--source include/have_binlog_format_mixed.inc
+
+--connection slave
+
+# Step1: Capture the current working replication state.
+# We need these to restore a clean environment after we've intentionally
+# "broken" the master.info file for the test.
+--let $master_host= query_get_value(SHOW SLAVE STATUS, Master_Host, 1)
+--let $master_port= query_get_value(SHOW SLAVE STATUS, Master_Port, 1)
+--let $master_user= query_get_value(SHOW SLAVE STATUS, Master_User, 1)
+
+--source include/stop_slave.inc
+
+# Suppress the err we expect to see in the log during this test.
+# The server will log these when it hits our new strict validation logic.
+call mtr.add_suppression("Error reading master configuration");
+call mtr.add_suppression("Failed to initialize the master info structure");
+call mtr.add_suppression("error connecting to master");
+
+--let $MYSQLD_DATADIR= `select @@datadir`
+
+# Step2: Simulate a corrupted master.info file.
+# We manually rewrite the file with "garbage" appended to numeric fields
+# (Port and Connect_Retry) to trigger the new validation check.
+--remove_file $MYSQLD_DATADIR/master.info
+--write_file $MYSQLD_DATADIR/master.info
+17
+master-bin.000001
+4
+127.0.0.1
+root
+
+3306abcdefghijklmnopqrstuvwxyz&10
+60
+0
+0
+
+
+
+0
+
+60.000abcdefghijklm
+1 1
+EOF
+
+# Step3: Restart the slave to force it to parse the corrupted file.
+--let $rpl_server_number= 2
+--source include/rpl_restart_server.inc
+
+--connection slave
+
+--echo # Verifying that trailing garbage causes parsing to fail.
+# If the fix works, the server should reject the bad port "3306abcdef..."
+# and fall back to the compiled-in default (3306).
+--let $port= query_get_value(SHOW SLAVE STATUS, Master_Port, 1)
+
+if ($port != 3306) {
+  --echo Error: The garbage in master.info was accepted! Port evaluated to $port.
+  --die "Test failed: Fix is not preventing garbage parsing."
+}
+
+# Step4: Cleanup and Restoration.
+# We remove the bad master.info and use CHANGE MASTER TO with our saved
+# parameters to restore the slave to its original state.
+--remove_file $MYSQLD_DATADIR/master.info
+
+--echo # Restoring the slave to original replication state
+--let $rpl_server_number= 2
+--source include/rpl_restart_server.inc
+
+--replace_result $master_port MASTER_PORT $master_host MASTER_HOST $master_user MASTER_USER
+--eval CHANGE MASTER TO MASTER_HOST='$master_host', MASTER_PORT=$master_port, MASTER_USER='$master_user'
+--source include/start_slave.inc
+
+--connection master
+--source include/rpl_end.inc
+

sql/slave.cc

@@ -1585,10 +1585,7 @@ int init_strvar_from_file(char *var, int max_size, IO_CACHE *f,
   DBUG_RETURN(1);
 }
 
-/*
-  when moving these functions to mysys, don't forget to
-  remove slave.cc from libmysqld/CMakeLists.txt
-*/
+
 int init_intvar_from_file(int* var, IO_CACHE* f, int default_val)
 {
   char buf[32];
@@ -1597,7 +1594,15 @@ int init_intvar_from_file(int* var, IO_CACHE* f, int default_val)
 
   if (my_b_gets(f, buf, sizeof(buf)))
   {
-    *var = atoi(buf);
+    char *endptr;
+    long val= strtol(buf, &endptr, 10);
+    
+    while (my_isspace(&my_charset_bin, *endptr))
+      endptr++;
+    if (*endptr != '\0')
+      DBUG_RETURN(1);
+
+    *var= (int) val;
     DBUG_RETURN(0);
   }
   else if (default_val)
@@ -1616,10 +1621,17 @@ int init_floatvar_from_file(float* var, IO_CACHE* f, float default_val)
 
   if (my_b_gets(f, buf, sizeof(buf)))
   {
-    if (sscanf(buf, "%f", var) != 1)
+    int bytes_read= 0;
+    if (sscanf(buf, "%f%n", var, &bytes_read) != 1)
       DBUG_RETURN(1);
-    else
-      DBUG_RETURN(0);
+    
+    char *endptr= buf + bytes_read;
+    while (my_isspace(&my_charset_bin, *endptr))
+      endptr++;
+    if (*endptr != '\0')
+      DBUG_RETURN(1);
+    
+    DBUG_RETURN(0);
   }
   else if (default_val != 0.0)
   {