c507ba55f5
PostgreSQL's src/port/open.c has always set bInheritHandle = TRUE
when opening files on Windows, making all file descriptors inheritable
by child processes. This meant the O_CLOEXEC flag, added to many call
sites by commit 1da569ca1f (v16), was silently ignored.
The original commit included a comment suggesting that our open()
replacement doesn't create inheritable handles, but it was a mis-
understanding of the code path. In practice, the code was creating
inheritable handles in all cases.
This hasn't caused widespread problems because most child processes
(archive_command, COPY PROGRAM, etc.) operate on file paths passed as
arguments rather than inherited file descriptors. Even if a child
wanted to use an inherited handle, it would need to learn the numeric
handle value, which isn't passed through our IPC mechanisms.
Nonetheless, the current behavior is wrong. It violates documented
O_CLOEXEC semantics, contradicts our own code comments, and makes
PostgreSQL behave differently on Windows than on Unix. It also creates
potential issues with future code or security auditing tools.
To fix, define O_CLOEXEC to _O_NOINHERIT in master, previously used by
O_DSYNC. We use different values in the back branches to preserve
existing values. In pgwin32_open_handle() we set bInheritHandle
according to whether O_CLOEXEC is specified, for the same atomic
semantics as POSIX in multi-threaded programs that create processes.
Backpatch-through: 16
Author: Bryan Green <dbryan.green@gmail.com>
Co-authored-by: Thomas Munro <thomas.munro@gmail.com> (minor adjustments)
Discussion: https://postgr.es/m/e2b16375-7430-4053-bda3-5d2194ff1880%40gmail.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.
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/.