[CRYPTO] api: Do not remove users unless new algorithm matches

As it is whenever a new algorithm with the same name is registered
users of the old algorithm will be removed so that they can take
advantage of the new algorithm.  This presents a problem when the
new algorithm is not equivalent to the old algorithm.  In particular,
the new algorithm might only function on top of the existing one.

Hence we should not remove users unless they can make use of the
new algorithm.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/algapi.c

@@ -84,36 +84,47 @@ static void crypto_destroy_instance(struct crypto_alg *alg)
 	crypto_tmpl_put(tmpl);
 }
 
+static void crypto_remove_spawn(struct crypto_spawn *spawn,
+				struct list_head *list,
+				struct list_head *secondary_spawns)
+{
+	struct crypto_instance *inst = spawn->inst;
+	struct crypto_template *tmpl = inst->tmpl;
+
+	list_del_init(&spawn->list);
+	spawn->alg = NULL;
+
+	if (crypto_is_dead(&inst->alg))
+		return;
+
+	inst->alg.cra_flags |= CRYPTO_ALG_DEAD;
+	if (!tmpl || !crypto_tmpl_get(tmpl))
+		return;
+
+	crypto_notify(CRYPTO_MSG_ALG_UNREGISTER, &inst->alg);
+	list_move(&inst->alg.cra_list, list);
+	hlist_del(&inst->list);
+	inst->alg.cra_destroy = crypto_destroy_instance;
+
+	list_splice(&inst->alg.cra_users, secondary_spawns);
+}
+
 static void crypto_remove_spawns(struct list_head *spawns,
-				 struct list_head *list)
+				 struct list_head *list, u32 new_type)
 {
 	struct crypto_spawn *spawn, *n;
+	LIST_HEAD(secondary_spawns);
 
 	list_for_each_entry_safe(spawn, n, spawns, list) {
-		struct crypto_instance *inst = spawn->inst;
-		struct crypto_template *tmpl = inst->tmpl;
-
-		list_del_init(&spawn->list);
-		spawn->alg = NULL;
-
-		if (crypto_is_dead(&inst->alg))
+		if ((spawn->alg->cra_flags ^ new_type) & spawn->mask)
 			continue;
 
-		inst->alg.cra_flags |= CRYPTO_ALG_DEAD;
-		if (!tmpl || !crypto_tmpl_get(tmpl))
-			continue;
+		crypto_remove_spawn(spawn, list, &secondary_spawns);
+	}
 
-		crypto_notify(CRYPTO_MSG_ALG_UNREGISTER, &inst->alg);
-		list_move(&inst->alg.cra_list, list);
-		hlist_del(&inst->list);
-		inst->alg.cra_destroy = crypto_destroy_instance;
-
-		if (!list_empty(&inst->alg.cra_users)) {
-			if (&n->list == spawns)
-				n = list_entry(inst->alg.cra_users.next,
-					       typeof(*n), list);
-			__list_splice(&inst->alg.cra_users, spawns->prev);
-		}
+	while (!list_empty(&secondary_spawns)) {
+		list_for_each_entry_safe(spawn, n, &secondary_spawns, list)
+			crypto_remove_spawn(spawn, list, &secondary_spawns);
 	}
 }
 
@@ -164,7 +175,7 @@ static int __crypto_register_alg(struct crypto_alg *alg,
 		    q->cra_priority > alg->cra_priority)
 			continue;
 
-		crypto_remove_spawns(&q->cra_users, list);
+		crypto_remove_spawns(&q->cra_users, list, alg->cra_flags);
 	}
 	
 	list_add(&alg->cra_list, &crypto_alg_list);
@@ -214,7 +225,7 @@ static int crypto_remove_alg(struct crypto_alg *alg, struct list_head *list)
 
 	crypto_notify(CRYPTO_MSG_ALG_UNREGISTER, alg);
 	list_del_init(&alg->cra_list);
-	crypto_remove_spawns(&alg->cra_users, list);
+	crypto_remove_spawns(&alg->cra_users, list, alg->cra_flags);
 
 	return 0;
 }
@@ -351,11 +362,12 @@ err:
 EXPORT_SYMBOL_GPL(crypto_register_instance);
 
 int crypto_init_spawn(struct crypto_spawn *spawn, struct crypto_alg *alg,
-		      struct crypto_instance *inst)
+		      struct crypto_instance *inst, u32 mask)
 {
 	int err = -EAGAIN;
 
 	spawn->inst = inst;
+	spawn->mask = mask;
 
 	down_write(&crypto_alg_sem);
 	if (!crypto_is_moribund(alg)) {
@@ -494,7 +506,8 @@ struct crypto_instance *crypto_alloc_instance(const char *name,
 		goto err_free_inst;
 
 	spawn = crypto_instance_ctx(inst);
-	err = crypto_init_spawn(spawn, alg, inst);
+	err = crypto_init_spawn(spawn, alg, inst,
+				CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC);
 
 	if (err)
 		goto err_free_inst;

include/crypto/algapi.h

@@ -51,6 +51,7 @@ struct crypto_spawn {
 	struct list_head list;
 	struct crypto_alg *alg;
 	struct crypto_instance *inst;
+	u32 mask;
 };
 
 struct crypto_queue {
@@ -103,7 +104,7 @@ void crypto_unregister_template(struct crypto_template *tmpl);
 struct crypto_template *crypto_lookup_template(const char *name);
 
 int crypto_init_spawn(struct crypto_spawn *spawn, struct crypto_alg *alg,
-		      struct crypto_instance *inst);
+		      struct crypto_instance *inst, u32 mask);
 void crypto_drop_spawn(struct crypto_spawn *spawn);
 struct crypto_tfm *crypto_spawn_tfm(struct crypto_spawn *spawn, u32 type,
 				    u32 mask);