From e92a111263b60a601420a69cb42bc1042e8ceb9a Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Sat, 7 Dec 2019 22:15:15 +0800 Subject: [PATCH] crypto: api - Fix race condition in crypto_spawn_alg 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: 6bfd48096ff8 ("[CRYPTO] api: Added spawns") Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- crypto/algapi.c | 16 +++++----------- crypto/api.c | 3 +-- crypto/internal.h | 1 - 3 files changed, 6 insertions(+), 14 deletions(-) diff --git a/crypto/algapi.c b/crypto/algapi.c index 1c704a9b7f70..5566650b2091 100644 --- a/crypto/algapi.c +++ b/crypto/algapi.c @@ -697,22 +697,16 @@ 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, diff --git a/crypto/api.c b/crypto/api.c index b5ad4cc1198a..c00af5ad1b16 100644 --- a/crypto/api.c +++ b/crypto/api.c @@ -346,13 +346,12 @@ static unsigned int crypto_ctxsize(struct crypto_alg *alg, u32 type, u32 mask) return len; } -void crypto_shoot_alg(struct crypto_alg *alg) +static void crypto_shoot_alg(struct crypto_alg *alg) { down_write(&crypto_alg_sem); alg->cra_flags |= CRYPTO_ALG_DYING; up_write(&crypto_alg_sem); } -EXPORT_SYMBOL_GPL(crypto_shoot_alg); struct crypto_tfm *__crypto_alloc_tfm(struct crypto_alg *alg, u32 type, u32 mask) diff --git a/crypto/internal.h b/crypto/internal.h index 93df7bec844a..e506a57e2243 100644 --- a/crypto/internal.h +++ b/crypto/internal.h @@ -68,7 +68,6 @@ void crypto_alg_tested(const char *name, int err); void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list, struct crypto_alg *nalg); void crypto_remove_final(struct list_head *list); -void crypto_shoot_alg(struct crypto_alg *alg); struct crypto_tfm *__crypto_alloc_tfm(struct crypto_alg *alg, u32 type, u32 mask); void *crypto_create_tfm(struct crypto_alg *alg,