Commit be924e0a authored by Eric Biggers's avatar Eric Biggers Committed by Herbert Xu
Browse files

crc-t10dif: use fallback in initial state 



Currently the crc-t10dif module starts out with the fallback disabled
and crct10dif_tfm == NULL.  crc_t10dif_mod_init() tries to allocate
crct10dif_tfm, and if it fails it enables the fallback.

This is backwards because it means that any call to crc_t10dif() prior
to module_init (which could theoretically happen from built-in code)
will crash rather than use the fallback as expected.  Also, it means
that if the initial tfm allocation fails, then the fallback stays
permanently enabled even if a crct10dif implementation is loaded later.

Change it to use the more logical solution of starting with the fallback
enabled, and disabling the fallback when a tfm gets allocated for the
first time.  This change also ends up simplifying the code.

Also take the opportunity to convert the code to use the new static_key
API, which is much less confusing than the old and deprecated one.

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 57b1aac1

lib/crc-t10dif.c

+10 −27
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ 
#include <linux/notifier.h>



static struct crypto_shash __rcu *crct10dif_tfm;

static struct static_key crct10dif_fallback __read_mostly;

static DEFINE_STATIC_KEY_TRUE(crct10dif_fallback);

static DEFINE_MUTEX(crc_t10dif_mutex);

static struct work_struct crct10dif_rehash_work;
@@ -26,7 +26,6 @@ static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, voi 
	struct crypto_alg *alg = data;



	if (val != CRYPTO_MSG_ALG_LOADED ||

	    static_key_false(&crct10dif_fallback) ||

	    strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))

		return 0;
@@ -41,10 +40,6 @@ static void crc_t10dif_rehash(struct work_struct *work) 
	mutex_lock(&crc_t10dif_mutex);

	old = rcu_dereference_protected(crct10dif_tfm,

					lockdep_is_held(&crc_t10dif_mutex));

	if (!old) {

		mutex_unlock(&crc_t10dif_mutex);

		return;

	}

	new = crypto_alloc_shash("crct10dif", 0, 0);

	if (IS_ERR(new)) {

		mutex_unlock(&crc_t10dif_mutex);
@@ -53,8 +48,12 @@ static void crc_t10dif_rehash(struct work_struct *work) 
	rcu_assign_pointer(crct10dif_tfm, new);

	mutex_unlock(&crc_t10dif_mutex);



	if (old) {

		synchronize_rcu();

		crypto_free_shash(old);

	} else {

		static_branch_disable(&crct10dif_fallback);

	}

}



static struct notifier_block crc_t10dif_nb = {
@@ -69,7 +68,7 @@ __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len) 
	} desc;

	int err;



	if (static_key_false(&crct10dif_fallback))

	if (static_branch_unlikely(&crct10dif_fallback))

		return crc_t10dif_generic(crc, buffer, len);



	rcu_read_lock();
@@ -93,18 +92,9 @@ EXPORT_SYMBOL(crc_t10dif); 


static int __init crc_t10dif_mod_init(void)

{

	struct crypto_shash *tfm;



	INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);

	crypto_register_notifier(&crc_t10dif_nb);

	mutex_lock(&crc_t10dif_mutex);

	tfm = crypto_alloc_shash("crct10dif", 0, 0);

	if (IS_ERR(tfm)) {

		static_key_slow_inc(&crct10dif_fallback);

		tfm = NULL;

	}

	RCU_INIT_POINTER(crct10dif_tfm, tfm);

	mutex_unlock(&crc_t10dif_mutex);

	crc_t10dif_rehash(&crct10dif_rehash_work);

	return 0;

}
@@ -124,20 +114,13 @@ static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp 
	const char *name;

	int len;



	if (static_key_false(&crct10dif_fallback))

	if (static_branch_unlikely(&crct10dif_fallback))

		return sprintf(buffer, "fallback\n");



	rcu_read_lock();

	tfm = rcu_dereference(crct10dif_tfm);

	if (!tfm) {

		len = sprintf(buffer, "init\n");

		goto unlock;

	}



	name = crypto_tfm_alg_driver_name(crypto_shash_tfm(tfm));

	len = sprintf(buffer, "%s\n", name);



unlock:

	rcu_read_unlock();



	return len;

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