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 3b9f5a0..f1d4ad0 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -28,9 +28,11 @@
struct crypto_shash *hmac_tfm;
struct crypto_shash *hash_tfm;
+static DEFINE_MUTEX(mutex);
+
static struct shash_desc *init_desc(const char type)
{
- int rc;
+ long rc;
char *algo;
struct crypto_shash **tfm;
struct shash_desc *desc;
@@ -44,12 +46,15 @@
}
if (*tfm == NULL) {
+ mutex_lock(&mutex);
+ if (*tfm)
+ goto out;
*tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(*tfm)) {
- pr_err("Can not allocate %s (reason: %ld)\n",
- algo, PTR_ERR(*tfm));
rc = PTR_ERR(*tfm);
+ pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
*tfm = NULL;
+ mutex_unlock(&mutex);
return ERR_PTR(rc);
}
if (type == EVM_XATTR_HMAC) {
@@ -57,9 +62,12 @@
if (rc) {
crypto_free_shash(*tfm);
*tfm = NULL;
+ mutex_unlock(&mutex);
return ERR_PTR(rc);
}
}
+out:
+ mutex_unlock(&mutex);
}
desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),