Further fixes for quoted-list GUC values in pg_dump and ruleutils.c.

Commits 742869946 et al turn out to be a couple bricks shy of a load.
We were dumping the stored values of GUC_LIST_QUOTE variables as they
appear in proconfig or setconfig catalog columns.  However, although that
quoting rule looks a lot like SQL-identifier double quotes, there are two
critical differences: empty strings ("") are legal, and depending on which
variable you're considering, values longer than NAMEDATALEN might be valid
too.  So the current technique fails altogether on empty-string list
entries (as reported by Steven Winfield in bug #15248) and it also risks
truncating file pathnames during dump/reload of GUC values that are lists
of pathnames.

To fix, split the stored value without any downcasing or truncation,
and then emit each element as a SQL string literal.

This is a tad annoying, because we now have three copies of the
comma-separated-string splitting logic in varlena.c as well as a fourth
one in dumputils.c.  (Not to mention the randomly-different-from-those
splitting logic in libpq...)  I looked at unifying these, but it would
be rather a mess unless we're willing to tweak the API definitions of
SplitIdentifierString, SplitDirectoriesString, or both.  That might be
worth doing in future; but it seems pretty unsafe for a back-patched
bug fix, so for now accept the duplication.

Back-patch to all supported branches, as the previous fix was.

Discussion: https://postgr.es/m/7585.1529435872@sss.pgh.pa.us

1 files changed, 26 insertions, 4 deletions

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 131d8685b73..7012c3355db 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -11955,14 +11955,36 @@ dumpFunc(Archive *fout, FuncInfo *finfo)
 		/*
 		 * 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.
+		 * proconfig array.  However, because the quoting rules used there
+		 * aren't exactly like SQL's, we have to break the list value apart
+		 * and then quote the elements as string literals.  (The elements may
+		 * be double-quoted as-is, but we can't just feed them to the SQL
+		 * parser; it would do the wrong thing with elements that are
+		 * zero-length or longer than NAMEDATALEN.)
+		 *
 		 * 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.
+		 * variable_is_guc_list_quote(), we'll do that; this makes it unsafe
+		 * to use GUC_LIST_QUOTE for extension variables.
 		 */
 		if (variable_is_guc_list_quote(configitem))
-			appendPQExpBufferStr(q, pos);
+		{
+			char	  **namelist;
+			char	  **nameptr;
+
+			/* Parse string into list of identifiers */
+			/* this shouldn't fail really */
+			if (SplitGUCList(pos, ',', &namelist))
+			{
+				for (nameptr = namelist; *nameptr; nameptr++)
+				{
+					if (nameptr != namelist)
+						appendPQExpBufferStr(q, ", ");
+					appendStringLiteralAH(q, *nameptr, fout);
+				}
+			}
+			pg_free(namelist);
+		}
 		else
 			appendStringLiteralAH(q, pos, fout);
 	}