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This commit adds a limit to the size of an XLogRecord at 1020MB, based
on a suggestion by Heikki Linnakangas. This counts for the overhead
needed by the XLogReader when allocating the memory it needs to read a
record in DecodeXLogRecordRequiredSpace(), based on the record size. An
assertion based on that is added to detect that any additions in the
XLogReader facilities would not cause any overflows. If that's ever the
case, the upper bound allowed would need to be adjusted.
Before this, it was possible for an external module to create WAL
records large enough to be assembled but not replayable, causing
failures when replaying such WAL records on standbys. One case
mentioned where this is possible is the in-core function
pg_logical_emit_message() (wrapper for LogLogicalMessage), that allows
to emit WAL records with an arbitrary amount of data potentially higher
than the replay limit of approximately 1GB (limit of a palloc, minus the
overhead needed by a XLogReader).
This commit is a follow-up of ffd1b6b that has added similar protections
for the block-level data. Here, the checks are extended to the whole
record length, mainrdata_len being extended from uint32 to uint64 with
the routines registering buffer and record data still limited to uint32
to minimize the checks when assembling a record. All the error messages
related to overflow checks are improved to provide more context about
the error happening.
Author: Matthias van de Meent
Reviewed-by: Andres Freund, Heikki Linnakangas, Michael Paquier
Discussion: https://postgr.es/m/CAEze2WgGiw+LZt+vHf8tWqB_6VxeLsMeoAuod0N=ij1q17n5pw@mail.gmail.com
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/.