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David Rowley e629846472 Fix incorrect accessing of pfree'd memory in Memoize
For pass-by-reference types, the code added in 0b053e78b, which aimed to
resolve a memory leak, was overly aggressive in resetting the per-tuple
memory context which could result in pfree'd memory being accessed
resulting in failing to find previously cached results in the hash
table.

What was happening was prepare_probe_slot() was switching to the
per-tuple memory context and calling ExecEvalExpr().  ExecEvalExpr() may
have required a memory allocation.  Both MemoizeHash_hash() and
MemoizeHash_equal() were aggressively resetting the per-tuple context
and after determining the hash value, the context would have gotten reset
before MemoizeHash_equal() was called.  This could have resulted in
MemoizeHash_equal() looking at pfree'd memory.

This is less likely to have caused issues on a production build as some
other allocation would have had to have reused the pfree'd memory to
overwrite it.  Otherwise, the original contents would have been intact.
However, this clearly caused issues on MEMORY_CONTEXT_CHECKING builds.

Author: Tender Wang, Andrei Lepikhov
Reported-by: Tender Wang (using SQLancer)
Reviewed-by: Andrei Lepikhov, Richard Guo, David Rowley
Discussion: https://postgr.es/m/CAHewXNnT6N6UJkya0z-jLFzVxcwGfeRQSfhiwA+NyLg-x8iGew@mail.gmail.com
Backpatch-through: 14, where Memoize was added
2024-03-11 18:19:56 +13:00
config Remove AIX support 2024-02-28 15:17:23 +04:00
contrib Fix deparsing of Consts in postgres_fdw ORDER BY 2024-03-11 12:27:11 +13:00
doc Doc: Warn about two_phase when altering a subscription's slot name. 2024-03-11 09:33:04 +05:30
src Fix incorrect accessing of pfree'd memory in Memoize 2024-03-11 18:19:56 +13:00
.cirrus.star Remove duplicate words in docs and code comments. 2023-10-09 09:18:47 +05:30
.cirrus.tasks.yml ci: Add test coverage of different pg_upgrade modes 2024-02-19 09:31:23 +01:00
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aclocal.m4 autoconf: Move export_dynamic determination to configure 2022-12-06 18:55:28 -08:00
configure Add --copy-file-range option to pg_upgrade. 2024-03-06 12:01:01 +13:00
configure.ac Add --copy-file-range option to pg_upgrade. 2024-03-06 12:01:01 +13:00
COPYRIGHT Update copyright for 2024 2024-01-03 20:49:05 -05:00
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HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
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README.md Convert README to Markdown. 2024-02-28 14:53:52 -06:00

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.

Copyright and license information can be found in the file COPYRIGHT.

General documentation about this version of PostgreSQL can be found at: https://www.postgresql.org/docs/devel/
In particular, information about building PostgreSQL from the source code can be found at: https://www.postgresql.org/docs/devel/installation.html

The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.