50a420bee0
If the substring start index and length overflow when added together, substring() misbehaved, either throwing a bogus "negative substring length" error on a case that should succeed, or failing to complain that a negative length is negative (and instead returning the whole string, in most cases). Unsurprisingly, the text, bytea, and bit variants of the function all had this issue. Rearrange the logic to ensure that negative lengths are always rejected, and add an overflow check to handle the other case. Also install similar guards into detoast_attr_slice() (nee heap_tuple_untoast_attr_slice()), since it's far from clear that no other code paths leading to that function could pass it values that would overflow. Patch by myself and Pavel Stehule, per bug #16804 from Rafi Shamim. Back-patch to v11. While these bugs are old, the common/int.h infrastructure for overflow-detecting arithmetic didn't exist before commit 4d6ad3125, and it doesn't seem like these misbehaviors are bad enough to justify developing a standalone fix for the older branches. Discussion: https://postgr.es/m/16804-f4eeeb6c11ba71d4@postgresql.org
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.