crypto: qat - add limit to linked list parsing

adf_copy_key_value_data() copies data from userland to kernel, based on
a linked link provided by userland. If userland provides a circular
list (or just a very long one) then it would drive a long loop where
allocation occurs in every loop. This could lead to low memory conditions.
Adding a limit to stop endless loop.

Signed-off-by: Adam Guerin <adam.guerin@intel.com>
Co-developed-by: Ciunas Bennett <ciunas.bennett@intel.com>
Signed-off-by: Ciunas Bennett <ciunas.bennett@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/qat/qat_common/adf_ctl_drv.c

@@ -16,6 +16,9 @@
 #include "adf_cfg_common.h"
 #include "adf_cfg_user.h"
 
+#define ADF_CFG_MAX_SECTION 512
+#define ADF_CFG_MAX_KEY_VAL 256
+
 #define DEVICE_NAME "qat_adf_ctl"
 
 static DEFINE_MUTEX(adf_ctl_lock);
@@ -137,10 +140,11 @@ static int adf_copy_key_value_data(struct adf_accel_dev *accel_dev,
 	struct adf_user_cfg_key_val key_val;
 	struct adf_user_cfg_key_val *params_head;
 	struct adf_user_cfg_section section, *section_head;
+	int i, j;
 
 	section_head = ctl_data->config_section;
 
-	while (section_head) {
+	for (i = 0; section_head && i < ADF_CFG_MAX_SECTION; i++) {
 		if (copy_from_user(&section, (void __user *)section_head,
 				   sizeof(*section_head))) {
 			dev_err(&GET_DEV(accel_dev),
@@ -156,7 +160,7 @@ static int adf_copy_key_value_data(struct adf_accel_dev *accel_dev,
 
 		params_head = section.params;
 
-		while (params_head) {
+		for (j = 0; params_head && j < ADF_CFG_MAX_KEY_VAL; j++) {
 			if (copy_from_user(&key_val, (void __user *)params_head,
 					   sizeof(key_val))) {
 				dev_err(&GET_DEV(accel_dev),