Date: Fri, 22 Mar 2024 09:36:19 -0400
From: Bruce Momjian <bruce@momjian.us>
To: walther@technowledgy.de
Cc: Thomas Munro <thomas.munro@gmail.com>,
	Peter Eisentraut <peter@eisentraut.org>,
	Christophe Pettus <xof@thebuild.com>,
	Andrew Dunstan <andrew@dunslane.net>,
	PostgreSQL Bugs <pgsql-bugs@lists.postgresql.org>,
	Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Regression tests fail with musl libc because libpq.so can't be
 loaded
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On Fri, Mar 22, 2024 at 09:33:38AM +0100, walther@technowledgy.de wrote:
> Bruce Momjian:
> > I suggest we use the #ifdef test to continue our existing behavior for
> > the libraries we know about, like glibc, and use the LD_* process title
> > truncation hack for libc's we don't recognize.
> > 
> > Attached is a prototype patch which implements this based on previous
> > patches.
> 
> The condition to check for linux/glibc in your patch is slightly off:
> 
>   #if ! defined(__linux__) || (! defined(__GLIBC__) && defined(__UCLIBC__ ))
> 
> should be
> 
>   #if defined(__linux__) && ! (defined(__GLIBC__) || defined(__UCLIBC__ ))
> 
> With the latter, it passes tests with musl.

Yes, my logic was wrong. Not sure what I was thinking, frankly.

I am not a big fan of negating a complex conditional, but would rather
pass the negation into the conditional, new patch attached.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.

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diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
index 5d829e6e483..c0786d30937 100644
--- a/src/backend/utils/misc/ps_status.c
+++ b/src/backend/utils/misc/ps_status.c
@@ -151,7 +151,32 @@ save_ps_display_args(int argc, char **argv)
 		for (i = 0; environ[i] != NULL; i++)
 		{
 			if (end_of_area + 1 == environ[i])
-				end_of_area = environ[i] + strlen(environ[i]);
+			{
+
+				/* Do this for Linux libc libraries that might be unsafe. */
+#if defined(__linux__) && (! defined(__GLIBC__) && ! defined(__UCLIBC__ ))
+				/*
+				 * If we see variables that the musl runtime linker is known
+				 * to stash pointers to, give up so we don't break later calls
+				 * to dlopen().
+				 */
+				if (strstr(environ[i], "LD_LIBRARY_PATH=") == environ[i] ||
+					strstr(environ[i], "LD_PRELOAD=") == environ[i])
+				{
+					/*
+					 * We can overwrite the name, but stop at the equals sign.
+					 * Future loops will not find contiguous space, but we
+					 * don't break early because we want to count the total
+					 * number.
+					 */
+					end_of_area = strchr(environ[i], '=');
+				}
+				else
+#endif
+				{
+					end_of_area = environ[i] + strlen(environ[i]);
+				}
+			}
 		}
 
 		ps_buffer = argv[0];

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