Fix uninitialized variable in dshash.c.

anarazel · anarazel · commit 0fb9e4ace5ce · 2017-09-18T17:43:37.000-07:00
A bugfix for commit 8c0d7ba. The code would have crashed if hashtable->size_log2 ever had the same value as hashtable->control->size_log2 by coincidence. Per Valgrind. Author: Thomas Munro Reported-By: Tomas Vondra Discussion: https://postgr.es/m/e72fb33c-4f31-f276-e972-263d9b59554d%402ndquadrant.com
diff --git a/src/backend/lib/dshash.c b/src/backend/lib/dshash.c
@@ -249,6 +249,7 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
 	}
 	hash_table->buckets = dsa_get_address(area,
 										  hash_table->control->buckets);
+	hash_table->size_log2 = hash_table->control->size_log2;
 
 	return hash_table;
 }
@@ -280,6 +281,14 @@ dshash_attach(dsa_area *area, const dshash_parameters *params,
 	hash_table->find_exclusively_locked = false;
 	Assert(hash_table->control->magic == DSHASH_MAGIC);
 
+	/*
+	 * These will later be set to the correct values by
+	 * ensure_valid_bucket_pointers(), at which time we'll be holding a
+	 * partition lock for interlocking against concurrent resizing.
+	 */
+	hash_table->buckets = NULL;
+	hash_table->size_log2 = 0;
+
 	return hash_table;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -249,6 +249,7 @@ dshash_create(dsa_area area, const dshash_parameters params, void *arg)`
`249`	`249`	`}`
`250`	`250`	`hash_table->buckets = dsa_get_address(area,`
`251`	`251`	`hash_table->control->buckets);`
	`252`	`+ hash_table->size_log2 = hash_table->control->size_log2;`
`252`	`253`
`253`	`254`	`return hash_table;`
`254`	`255`	`}`
`@@ -280,6 +281,14 @@ dshash_attach(dsa_area area, const dshash_parameters params,`
`280`	`281`	`hash_table->find_exclusively_locked = false;`
`281`	`282`	`Assert(hash_table->control->magic == DSHASH_MAGIC);`
`282`	`283`
	`284`	`+ /*`
	`285`	`+ * These will later be set to the correct values by`
	`286`	`+ * ensure_valid_bucket_pointers(), at which time we'll be holding a`
	`287`	`+ * partition lock for interlocking against concurrent resizing.`
	`288`	`+ */`
	`289`	`+ hash_table->buckets = NULL;`
	`290`	`+ hash_table->size_log2 = 0;`
	`291`	`+`
`283`	`292`	`return hash_table;`
`284`	`293`	`}`
`285`	`294`