linux-kernel - [PATCH v3 04/20] can: netlink: refactor can_validate

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Message-Id: <20250923-canxl-netlink-prep-v3-4-87a7684333f3@kernel.org>
Date: Tue, 23 Sep 2025 14:39:39 +0900
From: Vincent Mailhol <mailhol@...nel.org>
To: Marc Kleine-Budde <mkl@...gutronix.de>, 
 Oliver Hartkopp <socketcan@...tkopp.net>
Cc: Vincent Mailhol <mailhol@...nel.org>, 
 Stéphane Grosjean <stephane.grosjean@...-networks.com>, 
 Robert Nawrath <mbro1689@...il.com>, Minh Le <minh.le.aj@...esas.com>, 
 Duy Nguyen <duy.nguyen.rh@...esas.com>, linux-can@...r.kernel.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH v3 04/20] can: netlink: refactor can_validate_bittiming()

Whenever can_validate_bittiming() is called, it is always preceded by
some boilerplate code which was copy pasted all over the place. Move
that repeated code directly inside can_validate_bittiming().

Finally, the mempcy() is not needed: the nla attributes are four bytes
aligned which is just enough for struct can_bittiming. Add a
static_assert() to document that the alignment is correct and just use
the pointer returned by nla_data() as-is.

Signed-off-by: Vincent Mailhol <mailhol@...nel.org>
---
Changelog:

v2 -> v3:

  - add a static_assert() to prove that the alignment is correct.
---
 drivers/net/can/dev/netlink.c | 36 +++++++++++++++++-------------------
 1 file changed, 17 insertions(+), 19 deletions(-)

diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c
index 248f607e3864ffbda6f0b8daf4e2484179cf9cd5..13555253e789ec6ca9c8c30571c990ad6bfde770 100644
--- a/drivers/net/can/dev/netlink.c
+++ b/drivers/net/can/dev/netlink.c
@@ -36,13 +36,21 @@ static const struct nla_policy can_tdc_policy[IFLA_CAN_TDC_MAX + 1] = {
 	[IFLA_CAN_TDC_TDCF] = { .type = NLA_U32 },
 };
 
-static int can_validate_bittiming(const struct can_bittiming *bt,
-				  struct netlink_ext_ack *extack)
+static int can_validate_bittiming(struct nlattr *data[],
+				  struct netlink_ext_ack *extack,
+				  int ifla_can_bittiming)
 {
+	struct can_bittiming *bt;
+
+	if (!data[ifla_can_bittiming])
+		return 0;
+
+	static_assert(__alignof__(*bt) <= NLA_ALIGNTO);
+	bt = nla_data(data[ifla_can_bittiming]);
+
 	/* sample point is in one-tenth of a percent */
 	if (bt->sample_point >= 1000) {
 		NL_SET_ERR_MSG(extack, "sample point must be between 0 and 100%");
-
 		return -EINVAL;
 	}
 
@@ -105,14 +113,9 @@ static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 		}
 	}
 
-	if (data[IFLA_CAN_BITTIMING]) {
-		struct can_bittiming bt;
-
-		memcpy(&bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(bt));
-		err = can_validate_bittiming(&bt, extack);
-		if (err)
-			return err;
-	}
+	err = can_validate_bittiming(data, extack, IFLA_CAN_BITTIMING);
+	if (err)
+		return err;
 
 	if (is_can_fd) {
 		if (!data[IFLA_CAN_BITTIMING] || !data[IFLA_CAN_DATA_BITTIMING])
@@ -124,14 +127,9 @@ static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 			return -EOPNOTSUPP;
 	}
 
-	if (data[IFLA_CAN_DATA_BITTIMING]) {
-		struct can_bittiming bt;
-
-		memcpy(&bt, nla_data(data[IFLA_CAN_DATA_BITTIMING]), sizeof(bt));
-		err = can_validate_bittiming(&bt, extack);
-		if (err)
-			return err;
-	}
+	err = can_validate_bittiming(data, extack, IFLA_CAN_DATA_BITTIMING);
+	if (err)
+		return err;
 
 	return 0;
 }

-- 
2.49.1