MDEV-14929 - AddressSanitizer: memcpy-param-overlap in Field_longstr::compress

Handle overlaping "from" and Field_blob_compressed::value for compressed
blobs similarily to regular blobs.

mysql-test/main/column_compression.result

@@ -1360,3 +1360,16 @@ SELECT a, LENGTH(a) FROM t1;
 a	LENGTH(a)
 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	255
 DROP TABLE t1;
+#
+# MDEV-14929 - AddressSanitizer: memcpy-param-overlap in
+#              Field_longstr::compress
+#
+CREATE TABLE t1(b BLOB COMPRESSED);
+INSERT INTO t1 VALUES('foo'),('bar');
+SET SESSION optimizer_switch = 'derived_merge=off';
+SELECT * FROM ( SELECT * FROM t1 ) AS sq ORDER BY b;
+b
+bar
+foo
+SET SESSION optimizer_switch=DEFAULT;
+DROP TABLE t1;

mysql-test/main/column_compression.test

@@ -79,3 +79,15 @@ INSERT INTO t1 VALUES(REPEAT('a', 255));
 SET column_compression_threshold=DEFAULT;
 SELECT a, LENGTH(a) FROM t1;
 DROP TABLE t1;
+
+
+--echo #
+--echo # MDEV-14929 - AddressSanitizer: memcpy-param-overlap in
+--echo #              Field_longstr::compress
+--echo #
+CREATE TABLE t1(b BLOB COMPRESSED);
+INSERT INTO t1 VALUES('foo'),('bar');
+SET SESSION optimizer_switch = 'derived_merge=off';
+SELECT * FROM ( SELECT * FROM t1 ) AS sq ORDER BY b;
+SET SESSION optimizer_switch=DEFAULT;
+DROP TABLE t1;

sql/field.cc

@@ -8699,17 +8699,22 @@ int Field_blob_compressed::store(const char *from, size_t length,
 {
   ASSERT_COLUMN_MARKED_FOR_WRITE_OR_COMPUTED;
   uint to_length= (uint)MY_MIN(max_data_length(), field_charset->mbmaxlen * length + 1);
+  String tmp(from, length, cs);
   int rc;
 
+  if (from >= value.ptr() && from <= value.end() && tmp.copy(from, length, cs))
+    goto oom;
+
   if (value.alloc(to_length))
-  {
-    set_ptr((uint32) 0, NULL);
-    return -1;
-  }
+    goto oom;
 
-  rc= compress((char*) value.ptr(), &to_length, from, (uint)length, cs);
+  rc= compress((char*) value.ptr(), &to_length, tmp.ptr(), (uint) length, cs);
   set_ptr(to_length, (uchar*) value.ptr());
   return rc;
+
+oom:
+  set_ptr((uint32) 0, NULL);
+  return -1;
 }