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David Rowley 72b8507db2 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 18:21:48 +13:00
config Log LLVM library version in configure output. 2023-10-22 14:29:00 +13:00
contrib Fix deparsing of Consts in postgres_fdw ORDER BY 2024-03-11 12:28:40 +13:00
doc Doc: fix minor typos in two ECPG function descriptions. 2024-02-25 15:29:34 -05:00
src Fix incorrect accessing of pfree'd memory in Memoize 2024-03-11 18:21:48 +13:00
.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 Backpatch addition of .git-blame-ignore-revs 2022-08-05 19:36:24 +02:00
.gitattributes gitattributes: Add new entry to silence whitespace error 2021-06-05 07:57:31 +02:00
.gitignore Add portlock directory to .gitignore 2022-11-26 07:47:06 -05:00
COPYRIGHT Update copyright for 2024 2024-01-03 20:49:04 -05:00
GNUmakefile.in Remove temporary portlock directory during make [dist]clean. 2022-11-26 10:30:53 -05:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Don't unset MAKEFLAGS in non-GNU Makefile. 2019-06-25 09:36:21 +12:00
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 Probe $PROVE not $PERL while checking for modules needed by TAP tests. 2021-11-22 12:54:52 -05:00
configure Stamp 14.11. 2024-02-05 16:45:28 -05:00
configure.ac Stamp 14.11. 2024-02-05 16:45:28 -05:00

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/.