Revert "Secure Unix-domain sockets of "make check" temporary clusters."

About half of the buildfarm members use too-long directory names,
strongly suggesting that this approach is a dead end.

contrib/pg_upgrade/test.sh

@@ -25,6 +25,8 @@ case $testhost in
 	*)		LISTEN_ADDRESSES="" ;;
 esac
 
+POSTMASTER_OPTS="-F -c listen_addresses=$LISTEN_ADDRESSES"
+
 temp_root=$PWD/tmp_check
 
 if [ "$1" = '--install' ]; then
@@ -84,16 +86,13 @@ PGSERVICE="";         unset PGSERVICE
 PGSSLMODE="";         unset PGSSLMODE
 PGREQUIRESSL="";      unset PGREQUIRESSL
 PGCONNECT_TIMEOUT=""; unset PGCONNECT_TIMEOUT
+PGHOST="";            unset PGHOST
 PGHOSTADDR="";        unset PGHOSTADDR
 
-# Select a port number and socket directory, similarly to pg_regress.c
+# Select a non-conflicting port number, similarly to pg_regress.c
 PG_VERSION_NUM=`grep '#define PG_VERSION_NUM' $newsrc/src/include/pg_config.h | awk '{print $3}'`
 PGPORT=`expr $PG_VERSION_NUM % 16384 + 49152`
 export PGPORT
-PGHOST=${PG_REGRESS_SOCK_DIR-$PGDATA}
-export PGHOST
-
-POSTMASTER_OPTS="-F -c listen_addresses=$LISTEN_ADDRESSES -k \"$PGHOST\""
 
 i=0
 while psql -X postgres </dev/null 2>/dev/null

doc/src/sgml/regress.sgml

@@ -58,14 +58,21 @@ make check
 
   <warning>
    <para>
-    On systems lacking Unix-domain sockets, notably Windows, this test method
-    starts a temporary server configured to accept any connection originating
-    on the local machine.  Any local user can gain database superuser
-    privileges when connecting to this server, and could in principle exploit
-    all privileges of the operating-system user running the tests.  Therefore,
-    it is not recommended that you use <literal>make check</> on an affected
-    system shared with untrusted users.  Instead, run the tests after
-    completing the installation, as described in the next section.
+    This test method starts a temporary server, which is configured to accept
+    any connection originating on the local machine.  Any local user can gain
+    database superuser privileges when connecting to this server, and could
+    in principle exploit all privileges of the operating-system user running
+    the tests.  Therefore, it is not recommended that you use <literal>make
+    check</> on machines shared with untrusted users.  Instead, run the tests
+    after completing the installation, as described in the next section.
+   </para>
+
+   <para>
+    On Unix-like machines, this danger can be avoided if the temporary
+    server's socket file is made inaccessible to other users, for example
+    by running the tests in a protected chroot.  On Windows, the temporary
+    server opens a locally-accessible TCP socket, so filesystem protections
+    cannot help.
    </para>
   </warning>
 
@@ -104,17 +111,6 @@ make MAX_CONNECTIONS=10 check
 </screen>
     runs no more than ten tests concurrently.
    </para>
-
-   <para>
-    To protect your operating system user account, the test driver places the
-    server's socket in a relative subdirectory inaccessible to other users.
-    Since most systems constrain the length of socket paths well
-    below <literal>_POSIX_PATH_MAX</>, testing may fail to start from a
-    directory with a long name.  Work around this problem by pointing
-    the <envar>PG_REGRESS_SOCK_DIR</> environment variable to a substitute
-    socket directory having a shorter path.  On a multi-user system, give that
-    directory mode <literal>0700</>.
-   </para>
   </sect2>
 
   <sect2>

src/test/regress/pg_regress.c

@@ -109,7 +109,6 @@ static const char *progname;
 static char *logfilename;
 static FILE *logfile;
 static char *difffilename;
-static char *sockdir;
 
 static _resultmap *resultmap = NULL;
 
@@ -759,7 +758,8 @@ initialize_environment(void)
 		 * the wrong postmaster, or otherwise behave in nondefault ways. (Note
 		 * we also use psql's -X switch consistently, so that ~/.psqlrc files
 		 * won't mess things up.)  Also, set PGPORT to the temp port, and set
-		 * PGHOST depending on whether we are using TCP or Unix sockets.
+		 * or unset PGHOST depending on whether we are using TCP or Unix
+		 * sockets.
 		 */
 		unsetenv("PGDATABASE");
 		unsetenv("PGUSER");
@@ -771,23 +771,7 @@ initialize_environment(void)
 		if (hostname != NULL)
 			doputenv("PGHOST", hostname);
 		else
-		{
-			sockdir = getenv("PG_REGRESS_SOCK_DIR");
-			if (!sockdir)
-			{
-				/*
-				 * Since initdb creates the data directory with secure
-				 * permissions, we place the socket there.  This ensures no
-				 * other OS user can open our socket to exploit our use of
-				 * trust authentication.  Compared to using the compiled-in
-				 * DEFAULT_PGSOCKET_DIR, this also permits testing to work in
-				 * builds that relocate it to a directory not writable to the
-				 * build/test user.
-				 */
-				sockdir = psprintf("%s/data", temp_install);
-			}
-			doputenv("PGHOST", sockdir);
-		}
+			unsetenv("PGHOST");
 		unsetenv("PGHOSTADDR");
 		if (port != -1)
 		{
@@ -2281,11 +2265,10 @@ regression_main(int argc, char *argv[], init_function ifunc, test_function tfunc
 		 */
 		header(_("starting postmaster"));
 		snprintf(buf, sizeof(buf),
-				 SYSTEMQUOTE "\"%s/postgres\" -D \"%s/data\" -F%s "
-				 "-c \"listen_addresses=%s\" -k \"%s\" "
-				 "> \"%s/log/postmaster.log\" 2>&1" SYSTEMQUOTE,
-				 bindir, temp_install, debug ? " -d 5" : "",
-				 hostname ? hostname : "", sockdir ? sockdir : "",
+				 SYSTEMQUOTE "\"%s/postgres\" -D \"%s/data\" -F%s -c \"listen_addresses=%s\" > \"%s/log/postmaster.log\" 2>&1" SYSTEMQUOTE,
+				 bindir, temp_install,
+				 debug ? " -d 5" : "",
+				 hostname ? hostname : "",
 				 outputdir);
 		postmaster_pid = spawn_process(buf);
 		if (postmaster_pid == INVALID_PID)