evm: prevent racing during tfm allocation
There is a small chance of racing during tfm allocation.
This patch fixes it.
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 4ad657d..8738def 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -27,26 +27,35 @@
struct crypto_shash *hmac_tfm;
+static DEFINE_MUTEX(mutex);
+
static struct shash_desc *init_desc(void)
{
int rc;
struct shash_desc *desc;
if (hmac_tfm == NULL) {
+ mutex_lock(&mutex);
+ if (hmac_tfm)
+ goto out;
hmac_tfm = crypto_alloc_shash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(hmac_tfm)) {
pr_err("Can not allocate %s (reason: %ld)\n",
evm_hmac, PTR_ERR(hmac_tfm));
rc = PTR_ERR(hmac_tfm);
hmac_tfm = NULL;
+ mutex_unlock(&mutex);
return ERR_PTR(rc);
}
rc = crypto_shash_setkey(hmac_tfm, evmkey, evmkey_len);
if (rc) {
crypto_free_shash(hmac_tfm);
hmac_tfm = NULL;
+ mutex_unlock(&mutex);
return ERR_PTR(rc);
}
+out:
+ mutex_unlock(&mutex);
}
desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac_tfm),