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crypto: api - Do not zap spawn->alg

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Currently when a spawn is removed we will zap its alg field.
This is racy because the spawn could belong to an unregistered
instance which may dereference the spawn->alg field.

This patch fixes this by keeping spawn->alg constant and instead
adding a new spawn->dead field to indicate that a spawn is going
away.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Herbert Xu 2019-12-07 22:15:17 +08:00
parent 73669cc556
commit 4f87ee118d
2 changed files with 14 additions and 11 deletions
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24
crypto/algapi.c
View File

@ -93,15 +93,17 @@ static struct list_head *crypto_more_spawns(struct crypto_alg *alg,
if (!spawn)
return NULL;
n = list_next_entry(spawn, list);
if (spawn->alg && &n->list != stack && !n->alg)
n->alg = (n->list.next == stack) ? alg :
&list_next_entry(n, list)->inst->alg;
n = list_prev_entry(spawn, list);
list_move(&spawn->list, secondary_spawns);
return &n->list == stack ? top : &n->inst->alg.cra_users;
if (list_is_last(&n->list, stack))
return top;
n = list_next_entry(n, list);
if (!spawn->dead)
n->dead = false;
return &n->inst->alg.cra_users;
}
static void crypto_remove_instance(struct crypto_instance *inst,
@ -160,7 +162,7 @@ void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list,
if (&inst->alg == nalg)
break;
spawn->alg = NULL;
spawn->dead = true;
spawns = &inst->alg.cra_users;
/*
@ -179,7 +181,7 @@ void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list,
&secondary_spawns)));
list_for_each_entry_safe(spawn, n, &secondary_spawns, list) {
if (spawn->alg)
if (!spawn->dead)
list_move(&spawn->list, &spawn->alg->cra_users);
else
crypto_remove_instance(spawn->inst, list);
@ -670,7 +672,7 @@ EXPORT_SYMBOL_GPL(crypto_grab_spawn);
void crypto_drop_spawn(struct crypto_spawn *spawn)
{
down_write(&crypto_alg_sem);
if (spawn->alg)
if (!spawn->dead)
list_del(&spawn->list);
up_write(&crypto_alg_sem);
}
@ -682,7 +684,7 @@ static struct crypto_alg *crypto_spawn_alg(struct crypto_spawn *spawn)
down_read(&crypto_alg_sem);
alg = spawn->alg;
if (alg && !crypto_mod_get(alg)) {
if (!spawn->dead && !crypto_mod_get(alg)) {
alg->cra_flags |= CRYPTO_ALG_DYING;
alg = NULL;
}

1
include/crypto/algapi.h
View File

@ -70,6 +70,7 @@ struct crypto_spawn {
struct crypto_instance *inst;
const struct crypto_type *frontend;
u32 mask;
bool dead;
};
struct crypto_queue {