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Michael Paquier a06efbc3ac Fail hard on out-of-memory failures in xlogreader.c
This commit changes the WAL reader routines so as a FATAL for the
backend or exit(FAILURE) for the frontend is triggered if an allocation
for a WAL record decode fails in walreader.c, rather than treating this
case as bogus data, which would be equivalent to the end of WAL.  The
key is to avoid palloc_extended(MCXT_ALLOC_NO_OOM) in walreader.c,
relying on plain palloc() calls.

The previous behavior could make WAL replay finish too early than it
should.  For example, crash recovery finishing earlier may corrupt
clusters because not all the WAL available locally was replayed to
ensure a consistent state.  Out-of-memory failures would show up
randomly depending on the memory pressure on the host, but one simple
case would be to generate a large record, then replay this record after
downsizing a host, as Ethan Mertz originally reported.

This relies on bae868caf2, as the WAL reader routines now do the
memory allocation required for a record only once its header has been
fully read and validated, making xl_tot_len trustable.  Making the WAL
reader react differently on out-of-memory or bogus record data would
require ABI changes, so this is the safest choice for stable branches.
Also, it is worth noting that 3f1ce97346 has been using a plain
palloc() in this code for some time now.

Thanks to Noah Misch and Thomas Munro for the discussion.

Like the other commit, backpatch down to 12, leaving out v11 that will
be EOL'd soon.  The behavior of considering a failed allocation as bogus
data comes originally from 0ffe11abd3, where the record length
retrieved from its header was not entirely trustable.

Reported-by: Ethan Mertz
Discussion: https://postgr.es/m/ZRKKdI5-RRlta3aF@paquier.xyz
Backpatch-through: 12
2023-10-03 10:25:12 +09:00
config Fix typos in comments 2023-05-02 12:23:08 +09:00
contrib Fix the misuse of origin filter across multiple pg_logical_slot_get_changes() calls. 2023-09-27 14:20:57 +05:30
doc doc: fix link to ALTER GROUP 2023-09-29 14:32:16 -04:00
src Fail hard on out-of-memory failures in xlogreader.c 2023-10-03 10:25:12 +09:00
.cirrus.star ci: Prepare to make compute resources for CI configurable 2023-08-23 15:15:28 -07:00
.cirrus.tasks.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:28 -07:00
.cirrus.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:28 -07:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.git-blame-ignore-revs Add b334612b8 to .git-blame-ignore-revs. 2023-06-20 09:52:52 -04:00
.gitattributes gitattributes: Ignore imported pg_bsd_indent code for whitespace checks 2023-02-22 09:00:28 +01:00
.gitignore Update top-level .gitignore. 2022-12-04 15:23:00 -05:00
COPYRIGHT Update copyright for 2023 2023-01-02 15:00:37 -05:00
GNUmakefile.in Integrate pg_bsd_indent into our build/test infrastructure. 2023-02-12 12:22:21 -05:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Dynamically find correct installation docs in Makefile. 2022-01-19 14:48:25 +01:00
README Canonicalize some URLs 2020-02-10 20:47:50 +01:00
README.git Canonicalize some URLs 2020-02-10 20:47:50 +01:00
aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Stamp 16.0. 2023-09-11 16:10:09 -04:00
configure.ac Stamp 16.0. 2023-09-11 16:10:09 -04:00
meson.build meson: macos: Correct -exported_symbols_list syntax for Sonoma compat 2023-09-30 12:10:52 -07:00
meson_options.txt meson: Attach colon to keyword argument 2023-06-29 12:53:41 +02:00

README

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/.