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Commit 143b01d3 authored by Dmitry Kasatkin's avatar Dmitry Kasatkin Committed by James Morris
Browse files

evm: prevent racing during tfm allocation 



There is a small chance of racing during tfm allocation.
This patch fixes it.

Signed-off-by: default avatarDmitry Kasatkin <dmitry.kasatkin@intel.com>
Acked-by: default avatarMimi Zohar <zohar@us.ibm.com>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent 88d7ed35

security/integrity/evm/evm_crypto.c

+11 −3
Original line number Original line Diff line number Diff line
@@ -28,9 +28,11 @@ static int evmkey_len = MAX_KEY_SIZE; 
struct crypto_shash *hmac_tfm;

struct crypto_shash *hmac_tfm;

struct crypto_shash *hash_tfm;

struct crypto_shash *hash_tfm;





static DEFINE_MUTEX(mutex);



static struct shash_desc *init_desc(const char type)

static struct shash_desc *init_desc(const char type)

{

{

	int rc;

	long rc;

	char *algo;

	char *algo;

	struct crypto_shash **tfm;

	struct crypto_shash **tfm;

	struct shash_desc *desc;

	struct shash_desc *desc;
@@ -44,12 +46,15 @@ static struct shash_desc *init_desc(const char type) 
	}

	}





	if (*tfm == NULL) {

	if (*tfm == NULL) {

		mutex_lock(&mutex);

		if (*tfm)

			goto out;

		*tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);

		*tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);

		if (IS_ERR(*tfm)) {

		if (IS_ERR(*tfm)) {

			pr_err("Can not allocate %s (reason: %ld)\n",

			       algo, PTR_ERR(*tfm));

			rc = PTR_ERR(*tfm);

			rc = PTR_ERR(*tfm);

			pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);

			*tfm = NULL;

			*tfm = NULL;

			mutex_unlock(&mutex);

			return ERR_PTR(rc);

			return ERR_PTR(rc);

		}

		}

		if (type == EVM_XATTR_HMAC) {

		if (type == EVM_XATTR_HMAC) {
@@ -57,9 +62,12 @@ static struct shash_desc *init_desc(const char type) 
			if (rc) {

			if (rc) {

				crypto_free_shash(*tfm);

				crypto_free_shash(*tfm);

				*tfm = NULL;

				*tfm = NULL;

				mutex_unlock(&mutex);

				return ERR_PTR(rc);

				return ERR_PTR(rc);

			}

			}

		}

		}

out:

		mutex_unlock(&mutex);

	}

	}





	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),

	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),