MDEV-17153 server crash on repair table ... use_frm

data_file_length == 0 in mi_repair() is normal for REPAIR ... USE_FRM.
But in-file links (for blocks and deleted chain) must be compared with
the real file length to avoid spurious "link points outside datafile"
warnings and arbitrary block skipping.

mysql-test/r/repair.result

@@ -233,3 +233,24 @@ i
 UNLOCK TABLES;
 DROP TABLE t1;
 # End of 10.0 tests
+create table t1 (a int, b varchar(200));
+insert t1 select seq, repeat(200, seq) from seq_1_to_30;
+delete from t1 where a % 13 = 0;
+repair table t1 use_frm;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	warning	Number of rows changed from 0 to 28
+test.t1	repair	status	OK
+delete from t1 where a % 11 = 0;
+repair table t1 extended use_frm;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	warning	Number of rows changed from 0 to 26
+test.t1	repair	status	OK
+delete from t1 where a % 7 = 0;
+set myisam_repair_threads = 2;
+repair table t1 use_frm;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	warning	Number of rows changed from 0 to 22
+test.t1	repair	status	OK
+set myisam_repair_threads = default;
+drop table t1;
+# End of 10.2 tests

mysql-test/t/repair.test

 #
 # Test of repair table
 #
+--source include/have_sequence.inc
 --source include/default_charset.inc
 
 call mtr.add_suppression("character set is multi-byte");
@@ -246,3 +247,23 @@ UNLOCK TABLES;
 DROP TABLE t1;
 
 --echo # End of 10.0 tests
+
+#
+# MDEV-17153 server crash on repair table ... use_frm
+#
+# Note, this test case doesn't crash, but shows spurios warnings
+# unless the bug is fixed
+#
+create table t1 (a int, b varchar(200));
+insert t1 select seq, repeat(200, seq) from seq_1_to_30;
+delete from t1 where a % 13 = 0;
+repair table t1 use_frm;
+delete from t1 where a % 11 = 0;
+repair table t1 extended use_frm;
+delete from t1 where a % 7 = 0;
+set myisam_repair_threads = 2;
+repair table t1 use_frm;
+set myisam_repair_threads = default;
+drop table t1;
+
+--echo # End of 10.2 tests

storage/myisam/mi_check.c

@@ -1586,6 +1586,8 @@ int mi_repair(HA_CHECK *param, register MI_INFO *info,
   sort_param.filepos=new_header_length;
   param->read_cache.end_of_file=sort_info.filelength=
     mysql_file_seek(info->dfile, 0L, MY_SEEK_END, MYF(0));
+  if (info->state->data_file_length == 0)
+    info->state->data_file_length= sort_info.filelength;
   sort_info.dupp=0;
   sort_param.fix_datafile= (my_bool) (! rep_quick);
   sort_param.master=1;
@@ -2290,6 +2292,8 @@ int mi_repair_by_sort(HA_CHECK *param, register MI_INFO *info,
   sort_info.buff=0;
   param->read_cache.end_of_file=sort_info.filelength=
     mysql_file_seek(param->read_cache.file, 0L, MY_SEEK_END, MYF(0));
+  if (info->state->data_file_length == 0)
+    info->state->data_file_length= sort_info.filelength;
 
   sort_param.wordlist=NULL;
   init_alloc_root(&sort_param.wordroot, FTPARSER_MEMROOT_ALLOC_SIZE, 0,
@@ -2757,6 +2761,8 @@ int mi_repair_parallel(HA_CHECK *param, register MI_INFO *info,
   sort_info.buff=0;
   param->read_cache.end_of_file=sort_info.filelength=
     mysql_file_seek(param->read_cache.file, 0L, MY_SEEK_END, MYF(0));
+  if (info->state->data_file_length == 0)
+    info->state->data_file_length= sort_info.filelength;
 
   if (share->data_file_type == DYNAMIC_RECORD)
     rec_length=MY_MAX(share->base.min_pack_length+1,share->base.min_block_length);