iwlwifi: pnvm: don't kmemdup() more than we have

We shouldn't kmemdup() more data than we have, that might
cause the code to crash. Fix that by updating the length
before the kmemdup.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20211016114029.ab0e64c3fba9.Ic6a3295fc384750b51b4270bf0b7d94984a139f2@changeid

drivers/net/wireless/intel/iwlwifi/fw/pnvm.c

@@ -284,16 +284,15 @@ int iwl_pnvm_load(struct iwl_trans *trans,
 	/* First attempt to get the PNVM from BIOS */
 	package = iwl_uefi_get_pnvm(trans, &len);
 	if (!IS_ERR_OR_NULL(package)) {
+		/* we need only the data */
+		len -= sizeof(*package);
 		data = kmemdup(package->data, len, GFP_KERNEL);
 
 		/* free package regardless of whether kmemdup succeeded */
 		kfree(package);
 
-		if (data) {
-			/* we need only the data size */
-			len -= sizeof(*package);
+		if (data)
 			goto parse;
-		}
 	}
 
 	/* If it's not available, try from the filesystem */