linux-kernel - [PATCH] devlink: move DEVLINK_ATTR

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Message-Id: <20250708160652.1810573-1-arnd@kernel.org>
Date: Tue,  8 Jul 2025 18:06:43 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Jiri Pirko <jiri@...nulli.us>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Carolina Jubran <cjubran@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>,
	Cosmin Ratiu <cratiu@...dia.com>,
	Mark Bloch <mbloch@...dia.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Simon Horman <horms@...nel.org>,
	Joe Damato <jdamato@...tly.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] devlink: move DEVLINK_ATTR_MAX-sized array off stack

From: Arnd Bergmann <arnd@...db.de>

There are many possible devlink attributes, so having an array of them
on the stack can cause a warning for excessive stack usage:

net/devlink/rate.c: In function 'devlink_nl_rate_tc_bw_parse':
net/devlink/rate.c:382:1: error: the frame size of 1648 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]

Change this to dynamic allocation instead.

Fixes: 566e8f108fc7 ("devlink: Extend devlink rate API with traffic classes bandwidth management")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
I see that only two of the many array entries are actually used in this
function: DEVLINK_ATTR_RATE_TC_INDEX and DEVLINK_ATTR_RATE_TC_BW. If there
is an interface to extract just a single entry, using that would be
a little easier than the kcalloc().
---
 net/devlink/rate.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/net/devlink/rate.c b/net/devlink/rate.c
index d39300a9b3d4..e4083649748f 100644
--- a/net/devlink/rate.c
+++ b/net/devlink/rate.c
@@ -346,19 +346,23 @@ static int devlink_nl_rate_tc_bw_parse(struct nlattr *parent_nest, u32 *tc_bw,
 				       unsigned long *bitmap,
 				       struct netlink_ext_ack *extack)
 {
-	struct nlattr *tb[DEVLINK_ATTR_MAX + 1];
+	struct nlattr **tb;
 	u8 tc_index;
 	int err;
 
+	tb = kcalloc(DEVLINK_ATTR_MAX + 1, sizeof(struct nlattr *), GFP_KERNEL);
+	if (!tb)
+		return -ENOMEM;
 	err = nla_parse_nested(tb, DEVLINK_ATTR_MAX, parent_nest,
 			       devlink_dl_rate_tc_bws_nl_policy, extack);
 	if (err)
-		return err;
+		goto out;
 
+	err = -EINVAL;
 	if (!tb[DEVLINK_ATTR_RATE_TC_INDEX]) {
 		NL_SET_ERR_ATTR_MISS(extack, parent_nest,
 				     DEVLINK_ATTR_RATE_TC_INDEX);
-		return -EINVAL;
+		goto out;
 	}
 
 	tc_index = nla_get_u8(tb[DEVLINK_ATTR_RATE_TC_INDEX]);
@@ -366,19 +370,21 @@ static int devlink_nl_rate_tc_bw_parse(struct nlattr *parent_nest, u32 *tc_bw,
 	if (!tb[DEVLINK_ATTR_RATE_TC_BW]) {
 		NL_SET_ERR_ATTR_MISS(extack, parent_nest,
 				     DEVLINK_ATTR_RATE_TC_BW);
-		return -EINVAL;
+		goto out;
 	}
 
 	if (test_and_set_bit(tc_index, bitmap)) {
 		NL_SET_ERR_MSG_FMT(extack,
 				   "Duplicate traffic class index specified (%u)",
 				   tc_index);
-		return -EINVAL;
+		goto out;
 	}
 
 	tc_bw[tc_index] = nla_get_u32(tb[DEVLINK_ATTR_RATE_TC_BW]);
 
-	return 0;
+out:
+	kfree(tb);
+	return err;
 }
 
 static int devlink_nl_rate_tc_bw_set(struct devlink_rate *devlink_rate,
-- 
2.39.5