Fix mishandling of quoted-list GUC values in pg_dump and ruleutils.c.

Code that prints out the contents of setconfig or proconfig arrays in
SQL format needs to handle GUC_LIST_QUOTE variables differently from
other ones, because for those variables, flatten_set_variable_args()
already applied a layer of quoting.  The value can therefore safely
be printed as-is, and indeed must be, or flatten_set_variable_args()
will muck it up completely on reload.  For all other GUC variables,
it's necessary and sufficient to quote the value as a SQL literal.

We'd recognized the need for this long ago, but mis-analyzed the
need slightly, thinking that all GUC_LIST_INPUT variables needed
the special treatment.  That's actually wrong, since a valid value
of a LIST variable might include characters that need quoting,
although no existing variables accept such values.

More to the point, we hadn't made any particular effort to keep the
various places that deal with this up-to-date with the set of variables
that actually need special treatment, meaning that we'd do the wrong
thing with, for example, temp_tablespaces values.  This affects dumping
of SET clauses attached to functions, as well as ALTER DATABASE/ROLE SET
commands.

In ruleutils.c we can fix it reasonably honestly by exporting a guc.c
function that allows discovering the flags for a given GUC variable.
But pg_dump doesn't have easy access to that, so continue the old method
of having a hard-wired list of affected variable names.  At least we can
fix it to have just one list not two, and update the list to match
current reality.

A remaining problem with this is that it only works for built-in
GUC variables.  pg_dump's list obvious knows nothing of third-party
extensions, and even the "ask guc.c" method isn't bulletproof since
the relevant extension might not be loaded.  There's no obvious
solution to that, so for now, we'll just have to discourage extension
authors from inventing custom GUCs that need GUC_LIST_QUOTE.

This has been busted for a long time, so back-patch to all supported
branches.

Michael Paquier and Tom Lane, reviewed by Kyotaro Horiguchi and
Pavel Stehule

Discussion: https://postgr.es/m/20180111064900.GA51030@paquier.xyz

4 files changed, 41 insertions, 7 deletions

diff --git a/src/bin/pg_dump/dumputils.c b/src/bin/pg_dump/dumputils.c
index 8eb9e0c9926..46fc56e86b2 100644
--- a/src/bin/pg_dump/dumputils.c
+++ b/src/bin/pg_dump/dumputils.c
@@ -1522,3 +1522,26 @@ simple_string_list_member(SimpleStringList *list, const char *val)
 	}
 	return false;
 }
+
+/*
+ * Detect whether the given GUC variable is of GUC_LIST_QUOTE type.
+ *
+ * It'd be better if we could inquire this directly from the backend; but even
+ * if there were a function for that, it could only tell us about variables
+ * currently known to guc.c, so that it'd be unsafe for extensions to declare
+ * GUC_LIST_QUOTE variables anyway.  Lacking a solution for that, it doesn't
+ * seem worth the work to do more than have this list, which must be kept in
+ * sync with the variables actually marked GUC_LIST_QUOTE in guc.c.
+ */
+bool
+variable_is_guc_list_quote(const char *name)
+{
+	if (pg_strcasecmp(name, "temp_tablespaces") == 0 ||
+		pg_strcasecmp(name, "session_preload_libraries") == 0 ||
+		pg_strcasecmp(name, "shared_preload_libraries") == 0 ||
+		pg_strcasecmp(name, "local_preload_libraries") == 0 ||
+		pg_strcasecmp(name, "search_path") == 0)
+		return true;
+	else
+		return false;
+}
diff --git a/src/bin/pg_dump/dumputils.h b/src/bin/pg_dump/dumputils.h
index 24dc404ed1f..25da30284e8 100644
--- a/src/bin/pg_dump/dumputils.h
+++ b/src/bin/pg_dump/dumputils.h
@@ -75,4 +75,6 @@ extern void set_dump_section(const char *arg, int *dumpSections);
 extern void simple_string_list_append(SimpleStringList *list, const char *val);
 extern bool simple_string_list_member(SimpleStringList *list, const char *val);
 
+extern bool variable_is_guc_list_quote(const char *name);
+
 #endif   /* DUMPUTILS_H */
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 4501c8bed8e..523a12f3585 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -10149,11 +10149,15 @@ dumpFunc(Archive *fout, FuncInfo *finfo)
 		appendPQExpBuffer(q, "\n    SET %s TO ", fmtId(configitem));
 
 		/*
-		 * Some GUC variable names are 'LIST' type and hence must not be
-		 * quoted.
+		 * Variables that are marked GUC_LIST_QUOTE were already fully quoted
+		 * by flatten_set_variable_args() before they were put into the
+		 * proconfig array; we mustn't re-quote them or we'll make a mess.
+		 * Variables that are not so marked should just be emitted as simple
+		 * string literals.  If the variable is not known to
+		 * variable_is_guc_list_quote(), we'll do the latter; this makes it
+		 * unsafe to use GUC_LIST_QUOTE for extension variables.
 		 */
-		if (pg_strcasecmp(configitem, "DateStyle") == 0
-			|| pg_strcasecmp(configitem, "search_path") == 0)
+		if (variable_is_guc_list_quote(configitem))
 			appendPQExpBufferStr(q, pos);
 		else
 			appendStringLiteralAH(q, pos, fout);
diff --git a/src/bin/pg_dump/pg_dumpall.c b/src/bin/pg_dump/pg_dumpall.c
index fc2ee0a07e3..0b493c04830 100644
--- a/src/bin/pg_dump/pg_dumpall.c
+++ b/src/bin/pg_dump/pg_dumpall.c
@@ -1610,10 +1610,15 @@ makeAlterConfigCommand(PGconn *conn, const char *arrayitem,
 	appendPQExpBuffer(buf, "SET %s TO ", fmtId(mine));
 
 	/*
-	 * Some GUC variable names are 'LIST' type and hence must not be quoted.
+	 * Variables that are marked GUC_LIST_QUOTE were already fully quoted by
+	 * flatten_set_variable_args() before they were put into the setconfig
+	 * array; we mustn't re-quote them or we'll make a mess.  Variables that
+	 * are not so marked should just be emitted as simple string literals.  If
+	 * the variable is not known to variable_is_guc_list_quote(), we'll do the
+	 * latter; this makes it unsafe to use GUC_LIST_QUOTE for extension
+	 * variables.
 	 */
-	if (pg_strcasecmp(mine, "DateStyle") == 0
-		|| pg_strcasecmp(mine, "search_path") == 0)
+	if (variable_is_guc_list_quote(mine))
 		appendPQExpBufferStr(buf, pos + 1);
 	else
 		appendStringLiteralConn(buf, pos + 1, conn);