Disallow null category in crosstab_hash

jconway · jconway · commit 4a3cdb531be5 · 2019-12-23T13:34:12.000-05:00
While building a hash map of categories in load_categories_hash, resulting category names have not thus far been checked to ensure they are not null. Prior to pg12 null category names worked to the extent that they did not crash on some platforms. This is because those system libraries have an snprintf which can deal with being passed a null pointer argument for a string. But even in those cases null categories did nothing useful. And on some platforms it crashed. As of pg12, our own version of snprintf gets called, and it does not deal with null pointer arguments at all, and crashes consistently. Fix that by disallowing null categories. They never worked usefully, and no one has ever asked for them to work previously. Back-patch to all supported branches. Reported-By: Ireneusz Pluta Discussion: https://postgr.es/m/16176-7489719b05e4303c@postgresql.org
diff --git a/contrib/tablefunc/tablefunc.c b/contrib/tablefunc/tablefunc.c
@@ -761,6 +761,11 @@ load_categories_hash(char *cats_sql, MemoryContext per_query_ctx)
 
 			/* get the category from the current sql result tuple */
 			catname = SPI_getvalue(spi_tuple, spi_tupdesc, 1);
+			if (catname == NULL)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("provided \"categories\" SQL must " \
+								"not return NULL values")));
 
 			SPIcontext = MemoryContextSwitchTo(per_query_ctx);
 
