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Fix segfault when accessing fields/field_types on freed result #1427

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Fix segfault when accessing fields/field_types on freed result #1427

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15 changes: 15 additions & 0 deletions ext/mysql2/result.c
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Original file line number Diff line number Diff line change
Expand Up @@ -939,6 +939,9 @@ static VALUE rb_mysql_result_fetch_fields(VALUE self) {
}

if (wrapper->fields == Qnil) {
if (wrapper->resultFreed) {
rb_raise(cMysql2Error, "Result set has already been freed");
}
wrapper->numberOfFields = mysql_num_fields(wrapper->result);
wrapper->fields = rb_ary_new2(wrapper->numberOfFields);
}
Expand All @@ -958,6 +961,9 @@ static VALUE rb_mysql_result_fetch_field_types(VALUE self) {
GET_RESULT(self);

if (wrapper->fieldTypes == Qnil) {
if (wrapper->resultFreed) {
rb_raise(cMysql2Error, "Result set has already been freed");
}
wrapper->numberOfFields = mysql_num_fields(wrapper->result);
wrapper->fieldTypes = rb_ary_new2(wrapper->numberOfFields);
}
Expand Down Expand Up @@ -1192,6 +1198,7 @@ VALUE rb_mysql_result_to_obj(VALUE client, VALUE encoding, VALUE options, MYSQL_
wrapper->lastRowProcessed = 0;
wrapper->resultFreed = 0;
wrapper->result = r;
wrapper->numberOfFields = 0;
wrapper->fields = Qnil;
wrapper->fieldTypes = Qnil;
wrapper->rows = Qnil;
Expand Down Expand Up @@ -1221,6 +1228,14 @@ VALUE rb_mysql_result_to_obj(VALUE client, VALUE encoding, VALUE options, MYSQL_
* should be processed here. */
wrapper->is_streaming = (rb_hash_aref(options, sym_stream) == Qtrue ? 1 : 0);

/* Eagerly populate fields for non-streaming results to prevent
* segfault/error when accessing .fields on 0-row results that get freed
* after iteration completes but before .fields is accessed.
* See: https://github.com/brianmario/mysql2/issues/1426 */
if (r != NULL && !wrapper->is_streaming) {
rb_mysql_result_fetch_fields(obj);
}

return obj;
}

Expand Down