[PATCH v17 net-next 2/8] devlink: heap-allocate param fill buffers in devlink_nl_param_fill

[Ratheesh Kannoth]

devlink_nl_param_fill() kept two per-configuration-mode copies of
union devlink_param_value plus a struct devlink_param_gset_ctx on the
stack while building the Netlink reply. Allocate those with kcalloc()
and kzalloc_obj() instead, and route failures through a single cleanup
path so temporary buffers are always freed.

Signed-off-by: Ratheesh Kannoth <rkannoth@xxxxxxxxxxx>
---
 net/devlink/param.c | 62 +++++++++++++++++++++++++++++++++------------
 1 file changed, 46 insertions(+), 16 deletions(-)

diff --git a/net/devlink/param.c b/net/devlink/param.c
index 1a196d3a843d..bd3881349c60 100644
--- a/net/devlink/param.c
+++ b/net/devlink/param.c
@@ -304,56 +304,79 @@ static int devlink_nl_param_fill(struct sk_buff *msg, struct devlink *devlink,
 				 u32 portid, u32 seq, int flags,
 				 struct netlink_ext_ack *extack)
 {
-	union devlink_param_value default_value[DEVLINK_PARAM_CMODE_MAX + 1];
-	union devlink_param_value param_value[DEVLINK_PARAM_CMODE_MAX + 1];
 	bool default_value_set[DEVLINK_PARAM_CMODE_MAX + 1] = {};
 	bool param_value_set[DEVLINK_PARAM_CMODE_MAX + 1] = {};
 	const struct devlink_param *param = param_item->param;
-	struct devlink_param_gset_ctx ctx;
+	union devlink_param_value *default_value;
+	union devlink_param_value *param_value;
+	struct devlink_param_gset_ctx *ctx;
 	struct nlattr *param_values_list;
 	struct nlattr *param_attr;
 	void *hdr;
 	int err;
 	int i;
 
+	default_value = kcalloc(DEVLINK_PARAM_CMODE_MAX + 1,
+				sizeof(*default_value), GFP_KERNEL);
+	if (!default_value)
+		return -ENOMEM;
+
+	param_value = kcalloc(DEVLINK_PARAM_CMODE_MAX + 1,
+			      sizeof(*param_value), GFP_KERNEL);
+	if (!param_value) {
+		kfree(default_value);
+		return -ENOMEM;
+	}
+
+	ctx = kzalloc_obj(*ctx);
+	if (!ctx) {
+		kfree(param_value);
+		kfree(default_value);
+		return -ENOMEM;
+	}
+
 	/* Get value from driver part to driverinit configuration mode */
 	for (i = 0; i <= DEVLINK_PARAM_CMODE_MAX; i++) {
 		if (!devlink_param_cmode_is_supported(param, i))
 			continue;
 		if (i == DEVLINK_PARAM_CMODE_DRIVERINIT) {
-			if (param_item->driverinit_value_new_valid)
+			if (param_item->driverinit_value_new_valid) {
 				param_value[i] = param_item->driverinit_value_new;
-			else if (param_item->driverinit_value_valid)
+			} else if (param_item->driverinit_value_valid) {
 				param_value[i] = param_item->driverinit_value;
-			else
-				return -EOPNOTSUPP;
+			} else {
+				err = -EOPNOTSUPP;
+				goto get_put_fail;
+			}
 
 			if (param_item->driverinit_value_valid) {
 				default_value[i] = param_item->driverinit_default;
 				default_value_set[i] = true;
 			}
 		} else {
-			ctx.cmode = i;
-			err = devlink_param_get(devlink, param, &ctx, extack);
+			ctx->cmode = i;
+			err = devlink_param_get(devlink, param, ctx, extack);
 			if (err)
-				return err;
-			param_value[i] = ctx.val;
+				goto get_put_fail;
 
-			err = devlink_param_get_default(devlink, param, &ctx,
+			param_value[i] = ctx->val;
+
+			err = devlink_param_get_default(devlink, param, ctx,
 							extack);
 			if (!err) {
-				default_value[i] = ctx.val;
+				default_value[i] = ctx->val;
 				default_value_set[i] = true;
 			} else if (err != -EOPNOTSUPP) {
-				return err;
+				goto get_put_fail;
 			}
 		}
 		param_value_set[i] = true;
 	}
 
+	err = -EMSGSIZE;
 	hdr = genlmsg_put(msg, portid, seq, &devlink_nl_family, flags, cmd);
 	if (!hdr)
-		return -EMSGSIZE;
+		goto get_put_fail;
 
 	if (devlink_nl_put_handle(msg, devlink))
 		goto genlmsg_cancel;
@@ -393,6 +416,9 @@ static int devlink_nl_param_fill(struct sk_buff *msg, struct devlink *devlink,
 	nla_nest_end(msg, param_values_list);
 	nla_nest_end(msg, param_attr);
 	genlmsg_end(msg, hdr);
+	kfree(default_value);
+	kfree(param_value);
+	kfree(ctx);
 	return 0;
 
 values_list_nest_cancel:
@@ -401,7 +427,11 @@ static int devlink_nl_param_fill(struct sk_buff *msg, struct devlink *devlink,
 	nla_nest_cancel(msg, param_attr);
 genlmsg_cancel:
 	genlmsg_cancel(msg, hdr);
-	return -EMSGSIZE;
+get_put_fail:
+	kfree(default_value);
+	kfree(param_value);
+	kfree(ctx);
+	return err;
 }
 
 static void devlink_param_notify(struct devlink *devlink,
-- 
2.43.0