MDEV-20257 Server crashes in Grant_table_base::init_read_record upon crash-upgrade

when opening the `user` table separately, reset `thd->open_tables`
for the duration of open, otherwise auto-repair fallback-and-retry
will close *all* tables (but reopen only `user`)

1 files changed, 19 insertions, 0 deletions

diff --git a/mysql-test/main/grant_repair.test b/mysql-test/main/grant_repair.test
new file mode 100644
index 00000000000..0fc0edc7ded
--- /dev/null
+++ b/mysql-test/main/grant_repair.test
@@ -0,0 +1,19 @@
+#
+# MDEV-20257 Server crashes in Grant_table_base::init_read_record upon crash-upgrade
+#
+
+call mtr.add_suppression("/mysql/user");
+source include/switch_to_mysql_user.inc;
+
+let mysql_datadir=`select @@datadir`;
+flush tables;
+perl;
+  $f=$ENV{mysql_datadir} . '/mysql/user.MAI';
+  sysopen F, $f, 2  or die "sysopen $f: $!";
+  # set the open_count to 1, "table was not closed properly"
+  sysseek F, 24, O_RDWR or die "sysseek: $!";
+  syswrite F, 1, 1 or die "syswrite: $!";
+EOF
+flush privileges;
+
+source include/switch_to_mysql_global_priv.inc;