From 1f7237109951ebe8dc194461716443a5d8caf308 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Thu, 2 Apr 2015 22:31:22 +0800 Subject: [PATCH] crypto: api - Fix races in crypto_unregister_instance There are multiple problems in crypto_unregister_instance: 1) The cra_refcnt BUG_ON check is racy and can cause crashes. 2) The cra_refcnt check shouldn't exist at all. 3) There is no reference on tmpl to protect the tmpl->free call. This patch rewrites the function using crypto_remove_spawn which now morphs into crypto_remove_instance. Signed-off-by: Herbert Xu --- crypto/algapi.c | 23 +++++++---------------- 1 file changed, 7 insertions(+), 16 deletions(-) diff --git a/crypto/algapi.c b/crypto/algapi.c index 83b04e0884b1..0f1976eceb27 100644 --- a/crypto/algapi.c +++ b/crypto/algapi.c @@ -99,10 +99,9 @@ static struct list_head *crypto_more_spawns(struct crypto_alg *alg, return &n->list == stack ? top : &n->inst->alg.cra_users; } -static void crypto_remove_spawn(struct crypto_spawn *spawn, - struct list_head *list) +static void crypto_remove_instance(struct crypto_instance *inst, + struct list_head *list) { - struct crypto_instance *inst = spawn->inst; struct crypto_template *tmpl = inst->tmpl; if (crypto_is_dead(&inst->alg)) @@ -167,7 +166,7 @@ void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list, if (spawn->alg) list_move(&spawn->list, &spawn->alg->cra_users); else - crypto_remove_spawn(spawn, list); + crypto_remove_instance(spawn->inst, list); } } EXPORT_SYMBOL_GPL(crypto_remove_spawns); @@ -554,28 +553,20 @@ EXPORT_SYMBOL_GPL(crypto_register_instance); int crypto_unregister_instance(struct crypto_alg *alg) { - int err; struct crypto_instance *inst = (void *)alg; - struct crypto_template *tmpl = inst->tmpl; - LIST_HEAD(users); + LIST_HEAD(list); if (!(alg->cra_flags & CRYPTO_ALG_INSTANCE)) return -EINVAL; - BUG_ON(atomic_read(&alg->cra_refcnt) != 1); - down_write(&crypto_alg_sem); - hlist_del_init(&inst->list); - err = crypto_remove_alg(alg, &users); + crypto_remove_spawns(alg, &list, NULL); + crypto_remove_instance(inst, &list); up_write(&crypto_alg_sem); - if (err) - return err; - - tmpl->free(inst); - crypto_remove_final(&users); + crypto_remove_final(&list); return 0; } -- 2.20.1