This is a note to let you know that I've just added the patch titled
crypto: api - Fix race condition in crypto_spawn_alg
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
crypto-api-fix-race-condition-in-crypto_spawn_alg.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 73669cc556462f4e50376538d77ee312142e8a8a Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Sat, 7 Dec 2019 22:15:15 +0800
Subject: crypto: api - Fix race condition in crypto_spawn_alg
From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
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 <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
crypto/algapi.c | 16 +++++-----------
crypto/api.c | 3 +--
crypto/internal.h | 1 -
3 files changed, 6 insertions(+), 14 deletions(-)
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -663,22 +663,16 @@ 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,
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -355,13 +355,12 @@ static unsigned int crypto_ctxsize(struc
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)
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -87,7 +87,6 @@ void crypto_alg_tested(const char *name,
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,
Patches currently in stable-queue which might be from herbert@xxxxxxxxxxxxxxxxxxx are
queue-4.4/padata-remove-broken-queue-flushing.patch
queue-4.4/crypto-api-fix-race-condition-in-crypto_spawn_alg.patch
queue-4.4/crypto-picoxcell-adjust-the-position-of-tasklet_init-and-fix-missed-tasklet_kill.patch
queue-4.4/crypto-api-check-spawn-alg-under-lock-in-crypto_drop_spawn.patch
queue-4.4/crypto-pcrypt-do-not-clear-may_sleep-flag-in-original-request.patch
