and fix the use-after-free crash in RT #97625

dbdimp.c

@@ -1996,6 +1996,7 @@ static int my_login(pTHX_ SV* dbh, imp_dbh_t *imp_dbh)
   char* password;
   char* mysql_socket;
   int   result;
+  int fresh = 0;
   D_imp_xxh(dbh);
 
   /* TODO- resolve this so that it is set only if DBI is 1.607 */
@@ -2044,12 +2045,15 @@ static int my_login(pTHX_ SV* dbh, imp_dbh_t *imp_dbh)
 		  port ? port : "NULL");
 
   if (!imp_dbh->pmysql) {
+     fresh = 1;
      Newz(908, imp_dbh->pmysql, 1, MYSQL);
   }
   result = mysql_dr_connect(dbh, imp_dbh->pmysql, mysql_socket, host, port, user,
 			  password, dbname, imp_dbh) ? TRUE : FALSE;
-  if (!result)
+  if (fresh && !result) {
+      /* Prevent leaks, but do not free in case of a reconnect. See #97625 */
       Safefree(imp_dbh->pmysql);
+  }
   return result;
 }
 

t/rt85919-fetch-lost-connection.t

@@ -1,44 +1,61 @@
-use strict;
-use warnings;
-use DBI;
-use Test::More;
-use lib 't', '.';
-use vars qw($table $test_dsn $test_user $test_password $mdriver);
-require 'lib.pl';
-
-my $dbh;
-eval {$dbh= DBI->connect($test_dsn, $test_user, $test_password,
-                      { RaiseError => 1, PrintError => 0, AutoCommit => 0 });};
-if ($@) {
-    plan skip_all => "ERROR: $@. Can't continue test";
-}
-my $sth;
-my $ok = eval {
-    print "Connecting...\n";
-    ok( $sth = $dbh->do('SET wait_timeout = 5'), 'set wait_timeout');
-    print "Sleeping...\n";
-    sleep 7;
-    my $sql = 'SELECT 1';
-    if (1) {
-        ok( $sth = $dbh->prepare($sql), 'prepare SQL');
-        ok( $sth->execute(), 'execute SQL');
-        my @res = $sth->fetchrow_array();
-        is ( $res[0], undef, 'no rows returned');
-        ok( $sth->finish(), 'finish');
-        $sth = undef;
-    }
-    else {
-        print "Selecting...\n";
-        my @res = $dbh->selectrow_array($sql);
-    }
-    $dbh->disconnect();
-    $dbh = undef;
-    1;
-};
-if (not $ok) {
-    is ( $DBI::err, 2006, 'Received error 2006' );
-    is ( $DBI::errstr, 'MySQL server has gone away', 'Received MySQL server has gone away');
-    eval { $sth->finish(); } if defined $sth;
-    eval { $dbh->disconnect(); } if defined $dbh;
-}
-done_testing();
+use strict;
+use warnings;
+use DBI;
+use Test::More;
+use lib 't', '.';
+use vars qw($table $test_dsn $test_user $test_password $mdriver);
+require 'lib.pl';
+
+my $dbh;
+eval {$dbh= DBI->connect($test_dsn, $test_user, $test_password,
+                      { RaiseError => 1, PrintError => 0, AutoCommit => 0 });};
+if ($@) {
+    plan skip_all => "ERROR: $@. Can't continue test";
+}
+my $sth;
+my $ok = eval {
+    print "Connecting...\n";
+    ok( $sth = $dbh->do('SET wait_timeout = 5'), 'set wait_timeout');
+    print "Sleeping...\n";
+    sleep 7;
+    my $sql = 'SELECT 1';
+    if (1) {
+        ok( $sth = $dbh->prepare($sql), 'prepare SQL');
+        ok( $sth->execute(), 'execute SQL');
+        my @res = $sth->fetchrow_array();
+        is ( $res[0], undef, 'no rows returned');
+        ok( $sth->finish(), 'finish');
+        $sth = undef;
+    }
+    else {
+        print "Selecting...\n";
+        my @res = $dbh->selectrow_array($sql);
+    }
+    $dbh->disconnect();
+    $dbh = undef;
+    1;
+};
+if (not $ok) {
+    is ( $DBI::err, 2006, 'Received error 2006' );
+    is ( $DBI::errstr, 'MySQL server has gone away', 'Received MySQL server has gone away');
+    eval { $sth->finish(); } if defined $sth;
+    eval { $dbh->disconnect(); } if defined $dbh;
+}
+
+if (0) {
+  # This causes the use=after-free crash in RT #97625.
+  # different testcase by killing the service. which is of course
+  # not doable in a general testscript and highly system dependent.
+  system(qw(sudo service mysql start));
+  use DBI;
+  my $dbh = DBI->connect("DBI:mysql:database=test:port=3306");
+  $dbh->{mysql_auto_reconnect} = 1; # without this is works
+  my $select = sub { $dbh->do(q{SELECT 1}) for 1 .. 10; };
+  $select->();
+  system qw(sudo service mysql stop);
+  $select->();
+  ok(1, "dbh did not crash on closed connection");
+  system(qw(sudo service mysql start));
+}
+
+done_testing();