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Bug#50557 checksum table crashes server when used in performance_schema

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CHECKSUM TABLE for performance schema tables could cause uninitialized
memory reads.

The root cause is a design flaw in the implementation of
mysql_checksum_table(), which do not honor null fields.

However, fixing this bug in CHECKSUM TABLE is risky, as it can cause the
checksum value to change.

This fix implements a work around, to systematically reset fields values
even for null fields, so that the field memory representation is always
initialized with a known value.
This commit is contained in:
Marc Alff 2010-09-17 13:03:09 -06:00
parent fdb40d42e5
commit 14ac8c79ff
1 changed files with 12 additions and 0 deletions
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12
storage/perfschema/pfs_engine_table.cc
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@ -223,6 +223,8 @@ int PFS_engine_table::read_row(TABLE *table,
Field **fields)
{
my_bitmap_map *org_bitmap;
Field *f;
Field **fields_reset;
/*
Make sure the table structure is as expected before mapping
@ -240,6 +242,16 @@ int PFS_engine_table::read_row(TABLE *table,
/* We internally write to Fields to support the read interface */
org_bitmap= dbug_tmp_use_all_columns(table, table->write_set);
/*
Some callers of the storage engine interface do not honor the
f->is_null() flag, and will attempt to read the data itself.
A known offender is mysql_checksum_table().
For robustness, reset every field.
*/
for (fields_reset= fields; (f= *fields_reset) ; fields_reset++)
f->reset();
int result= read_row_values(table, buf, fields, read_all);
dbug_tmp_restore_column_map(table->write_set, org_bitmap);