linux-kernel - [PATCH] [v2] devlink: move DEVLINK_ATTR

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Message-Id: <20250709145908.259213-1-arnd@kernel.org>
Date: Wed,  9 Jul 2025 16:59:00 +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>,
	Mark Bloch <mbloch@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>,
	Carolina Jubran <cjubran@...dia.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Simon Horman <horms@...nel.org>,
	Cosmin Ratiu <cratiu@...dia.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] [v2] 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().

v2: use __free() helper to simplify cleanup
---
 net/devlink/rate.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/devlink/rate.c b/net/devlink/rate.c
index d39300a9b3d4..3c4689c6cefb 100644
--- a/net/devlink/rate.c
+++ b/net/devlink/rate.c
@@ -346,10 +346,14 @@ 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 __free(kfree) = NULL;
 	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)
-- 
2.39.5