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crypto: api - Fix race condition in crypto_spawn_alg

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commit 73669cc556462f4e50376538d77ee312142e8a8a upstream.

The function crypto_spawn_alg is racy because it drops the lock
before shooting the dying algorithm.  The algorithm could disappear
altogether before we shoot it.

This patch fixes it by moving the shooting into the locked section.

Fixes: 6bfd48096f ("[CRYPTO] api: Added spawns")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Herbert Xu 2019-12-07 22:15:15 +08:00 • committed by Greg Kroah-Hartman
parent df3168ec13
commit 96ad8d508f
3 changed files with 6 additions and 14 deletions
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16
crypto/algapi.c
View file

@ -662,22 +662,16 @@ EXPORT_SYMBOL_GPL(crypto_drop_spawn);
static struct crypto_alg *crypto_spawn_alg(struct crypto_spawn *spawn)
{
struct crypto_alg *alg;
struct crypto_alg *alg2;
down_read(&crypto_alg_sem);
alg = spawn->alg;
alg2 = alg;
if (alg2)
alg2 = crypto_mod_get(alg2);
if (alg && !crypto_mod_get(alg)) {
alg->cra_flags |= CRYPTO_ALG_DYING;
alg = NULL;
}
up_read(&crypto_alg_sem);
if (!alg2) {
if (alg)
crypto_shoot_alg(alg);
return ERR_PTR(-EAGAIN);
}
return alg;
return alg ?: ERR_PTR(-EAGAIN);
}
struct crypto_tfm *crypto_spawn_tfm(struct crypto_spawn *spawn, u32 type,