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crypto: api - Fix races in crypto_unregister_instance

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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 <herbert@gondor.apana.org.au>
This commit is contained in:
Herbert Xu 2015-04-02 22:31:22 +08:00
parent 13cf394c8c
commit 1f72371099
1 changed files with 7 additions and 16 deletions
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23
crypto/algapi.c
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@ -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;
}