0001-Don-t-clobber-LD_-environment-variables.patch

From 1b2aa67cc1e692065f6cc18b70ee49131ec4682a Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Tue, 19 Mar 2024 00:25:34 +1300
Subject: [PATCH] Don't clobber LD_* environment variables.

Our PS_USE_CLOBBER_ARGV code relocates the environment, which itself is
allowed, in order to steal the old space to make a bigger argv[0] for
ps/top to show, which is probably formally undefined behavior.

Unfortunately that corrupts musl's copy of LD_LIBRARY_PATH if set,
because it stashes a pointer to the initial value before main() begins.
It probably doesn't matter for installed servers but breaks the
regression tests.

Here we look out for variables named LD_* while computing how much space
to steal, so we can avoid clobbering them.  No change in behaviour if
not found, but otherwise you might potentially get ps status messages
truncated to a smaller size than before depending on the length of
preceding clobberable variables.  There doesn't seem to be a nice way to
distinguish musl from glibc, and the truncation size shouldn't be too
small or at least has an easy mitigation: define a dummy variable.

Reported-by: Wolfgang Walther <walther@technowledgy.de>
Discussion: https://postgr.es/m/fddd1cd6-dc16-40a2-9eb5-d7fef2101488%40technowledgy.de
---
 src/backend/utils/misc/ps_status.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
index 5d829e6e48..782dea352e 100644
--- a/src/backend/utils/misc/ps_status.c
+++ b/src/backend/utils/misc/ps_status.c
@@ -146,11 +146,16 @@ save_ps_display_args(int argc, char **argv)
 		}
 
 		/*
-		 * check for contiguous environ strings following argv
+		 * Check for contiguous environ strings following argv, but skip
+		 * LD_* variables that the runtime linker might be interested in.  The
+		 * musl libc implementation is known to stash pointers directly to
+		 * their values in the initial environment, assuming them to be
+		 * immutable.
 		 */
 		for (i = 0; environ[i] != NULL; i++)
 		{
-			if (end_of_area + 1 == environ[i])
+			if (end_of_area + 1 == environ[i] &&
+				strncmp(environ[i], "LD_", 3) != 0)
 				end_of_area = environ[i] + strlen(environ[i]);
 		}
 
-- 
2.39.3 (Apple Git-146)