crypto: qat - Fix invalid synchronization between register/unregister sym algs

commit 6f043b50 upstream.

The synchronization method used atomic was bogus.
Use a proper synchronization with mutex.
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
[ kamal: backport to 3.19-stable: context ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/crypto/qat/qat_common/qat_algs.c

@@ -73,7 +73,8 @@
 			ICP_QAT_HW_CIPHER_KEY_CONVERT, \
 			ICP_QAT_HW_CIPHER_DECRYPT)
 
-static atomic_t active_dev;
+static DEFINE_MUTEX(algs_lock);
+static unsigned int active_devs;
 
 struct qat_alg_buf {
 	uint32_t len;
@@ -962,27 +963,34 @@ static struct crypto_alg qat_algs[] = { {
 
 int qat_algs_register(void)
 {
-	if (atomic_add_return(1, &active_dev) == 1) {
+	int ret = 0;
+
+	mutex_lock(&algs_lock);
+	if (++active_devs == 1) {
 		int i;
 
 		for (i = 0; i < ARRAY_SIZE(qat_algs); i++)
 			qat_algs[i].cra_flags =	CRYPTO_ALG_TYPE_AEAD |
 						CRYPTO_ALG_ASYNC;
-		return crypto_register_algs(qat_algs, ARRAY_SIZE(qat_algs));
+		ret = crypto_register_algs(qat_algs, ARRAY_SIZE(qat_algs));
 	}
-	return 0;
+	mutex_unlock(&algs_lock);
+	return ret;
 }
 
 int qat_algs_unregister(void)
 {
-	if (atomic_sub_return(1, &active_dev) == 0)
-		return crypto_unregister_algs(qat_algs, ARRAY_SIZE(qat_algs));
-	return 0;
+	int ret = 0;
+
+	mutex_lock(&algs_lock);
+	if (--active_devs == 0)
+		ret = crypto_unregister_algs(qat_algs, ARRAY_SIZE(qat_algs));
+	mutex_unlock(&algs_lock);
+	return ret;
 }
 
 int qat_algs_init(void)
 {
-	atomic_set(&active_dev, 0);
 	crypto_get_default_rng();
 	return 0;
 }