From 73669cc556462f4e50376538d77ee312142e8a8a Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Sat, 7 Dec 2019 22:15:15 +0800 Subject: crypto: api - Fix race condition in crypto_spawn_alg 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: 6bfd48096ff8 ("[CRYPTO] api: Added spawns") Signed-off-by: Herbert Xu --- crypto/algapi.c | 16 +++++----------- 1 file changed, 5 insertions(+), 11 deletions(-) (limited to 'crypto/algapi.c') diff --git a/crypto/algapi.c b/crypto/algapi.c index 9ecb4a57b342..54e844ad9364 100644 --- a/crypto/algapi.c +++ b/crypto/algapi.c @@ -679,22 +679,16 @@ 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); - up_read(&crypto_alg_sem); - - if (!alg2) { - if (alg) - crypto_shoot_alg(alg); - return ERR_PTR(-EAGAIN); + if (alg && !crypto_mod_get(alg)) { + alg->cra_flags |= CRYPTO_ALG_DYING; + alg = NULL; } + up_read(&crypto_alg_sem); - return alg; + return alg ?: ERR_PTR(-EAGAIN); } struct crypto_tfm *crypto_spawn_tfm(struct crypto_spawn *spawn, u32 type, -- cgit v1.2.3