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MDEV-11646 main.myisam, maria.maria, main.mix2_myisam, main.myisampac…

…k, main.mrr_icp_extra fail in buildbot with valgrind (Syscall param pwrite64(buf) points to uninitialised byte(s))

If the table has a varchar column and a forced fixed for format
(as in varchar.inc), Field_varstring::store() will only store the
actual number of bytes, not padded, in the record[0].

That is, on inserts a part of record[0] can be uninitialized.

Fix: initialize record[0] when a TABLE is created, it doesn't matter
what kind of garbage can be in this unused/invisible part of the
record, as long as it's not some random memory contents
(that can contain sensitive data).
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vuvova committed Jun 23, 2017
1 parent a1e51e7 commit b503b1c0edaa976e90b9bf3339677a710752e58a
Showing with 2 additions and 16 deletions.
  1. +1 −6 sql/sql_insert.cc
  2. +1 −10 sql/table.cc
@@ -970,12 +970,7 @@ bool mysql_insert(THD *thd,TABLE_LIST *table_list,
be overwritten by fill_record() anyway (and fill_record() does not
use default values in this case).
*/
#ifdef HAVE_valgrind
if (table->file->ha_table_flags() && HA_RECORD_MUST_BE_CLEAN_ON_WRITE)
restore_record(table,s->default_values); // Get empty record
else
#endif
table->record[0][0]= share->default_values[0];
table->record[0][0]= share->default_values[0];

/* Fix undefined null_bits. */
if (share->null_bytes > 1 && share->last_null_bit_pos)
@@ -4150,16 +4150,7 @@ void TABLE::init(THD *thd, TABLE_LIST *tl)

DBUG_ASSERT(key_read == 0);

/* mark the record[0] uninitialized */
TRASH(record[0], s->reclength);

/*
Initialize the null marker bits, to ensure that if we are doing a read
of only selected columns (like in keyread), all null markers are
initialized.
*/
memset(record[0], 255, s->null_bytes);
memset(record[1], 255, s->null_bytes);
restore_record(this, s->default_values);

/* Tables may be reused in a sub statement. */
DBUG_ASSERT(!file->extra(HA_EXTRA_IS_ATTACHED_CHILDREN));

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