From nobody Thu Oct 2 03:30:35 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 924E830F7FD; Tue, 23 Sep 2025 06:37:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758609452; cv=none; b=YQaWo8qS8b7JZWS1590lzf5Tzex4dyIBfBPxnZtLX00PO3uiQKn3WH4R5cZ5/oOo9G9utchXx2XJba7bF/HwrIJ9mq4wJsEWN/QC8lWBLgfPocUn8OCV4oWxk/v0MRwj2ywYWv9rXcAg58iz3SJMaHIVgTDJLZnFJXZInDymjaI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758609452; c=relaxed/simple; bh=drdc6vhp0itUxR+RtAgDkGEMcboFw0v8IhKD5qU7Q48=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=cwz+y4bSC9wL7drOJ27YJBGO22Hz4n//RWJLnOoJmLBHdbtFcpZ4x8s7Vr1FI6vYUs+dKLj15YxRPWlDV79Ndt4aFOSX1hOMm6cx3Pmtdyi0ag2aSUF4DMyGxn7gYhDZ2rrEu4yf6NKk960CMyQXqQccSEPeSNSgpvpUMOPgJbU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YlukZXZg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YlukZXZg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB890C4CEF7; Tue, 23 Sep 2025 06:37:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758609452; bh=drdc6vhp0itUxR+RtAgDkGEMcboFw0v8IhKD5qU7Q48=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=YlukZXZgC0+6P60oTZMuEfX5mGELp3e0pSWPSnAMJ30tLRxb1HasEIwHs9bmz/pi+ uJb37ZR8HC5EnX8v6wC8m1dtLMv0YWDeoVVDMs8+CaLrHAtsT6awppwrbzmMS9ERrZ VdF26bApfWJ3o951iDsXq+sqGSiYx3dRF2PnTro6s5E5FqY6PaSYSZEWiiE8zkPI+5 NCSbJkNhXFzDiKxXyzr7SF8rSX3nHwtgUVOnS15sMG1SzEM7RFKK6r+1BxCgtFUPL0 apFNB3+SA6lTa39oZDNE9+Ru7eU34kzHH3oPWrQeAji4JSDsZWCtQ7G0ISTVFSmORL nSvlct/fIM7qQ== From: Vincent Mailhol Date: Tue, 23 Sep 2025 15:37:08 +0900 Subject: [PATCH v3 1/4] can: annotate mtu accesses with READ_ONCE() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250923-can-fix-mtu-v3-1-581bde113f52@kernel.org> References: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> In-Reply-To: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> To: Oliver Hartkopp , Marc Kleine-Budde Cc: linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Mailhol X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2365; i=mailhol@kernel.org; h=from:subject:message-id; bh=drdc6vhp0itUxR+RtAgDkGEMcboFw0v8IhKD5qU7Q48=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDBmXHOSarosW6u833eFd9PWDSPgJ6UUrg6xE9qpxLX2ym ZFjW+brjlIWBjEuBlkxRZZl5ZzcCh2F3mGH/lrCzGFlAhnCwMUpABOR2MLwP9zqYYzCtaczQyyN a4TtslZmT3TeffbVKkZD/yiR577u5gx/hbVZdqwteLHSY/H0x789/lh3mW8K3FEw6evSOJH/mZ+ u8wAA X-Developer-Key: i=mailhol@kernel.org; a=openpgp; fpr=ED8F700574E67F20E574E8E2AB5FEB886DBB99C2 As hinted in commit 501a90c94510 ("inet: protect against too small mtu values."), net_device->mtu is vulnerable to race conditions if it is written and read without holding the RTNL. At the moment, all the writes are done while the interface is down, either in the devices' probe() function or in can_changelink(). So there are no such issues yet. But upcoming changes will allow to modify the MTU while the CAN XL devices are up. In preparation to the introduction of CAN XL, annotate all the net_device->mtu accesses which are not yet guarded by the RTNL with a READ_ONCE(). Note that all the write accesses are already either guarded by the RTNL or are already annotated and thus need no changes. Signed-off-by: Vincent Mailhol --- net/can/af_can.c | 2 +- net/can/isotp.c | 2 +- net/can/raw.c | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/net/can/af_can.c b/net/can/af_can.c index b2387a46794a576973f3d865a5ca8e2ba696d167..770173d8db42813d5c085248d1b= cf5fbe717955b 100644 --- a/net/can/af_can.c +++ b/net/can/af_can.c @@ -221,7 +221,7 @@ int can_send(struct sk_buff *skb, int loop) } =20 /* Make sure the CAN frame can pass the selected CAN netdevice. */ - if (unlikely(skb->len > skb->dev->mtu)) { + if (unlikely(skb->len > READ_ONCE(skb->dev->mtu))) { err =3D -EMSGSIZE; goto inval_skb; } diff --git a/net/can/isotp.c b/net/can/isotp.c index dee1412b3c9c1ffcfc43a109b448701459fcf8b9..74ee1e52249b232813a06c5d2c6= e404a38dce990 100644 --- a/net/can/isotp.c +++ b/net/can/isotp.c @@ -1313,7 +1313,7 @@ static int isotp_bind(struct socket *sock, struct soc= kaddr *uaddr, int len) err =3D -ENODEV; goto out; } - if (dev->mtu < so->ll.mtu) { + if (READ_ONCE(dev->mtu) < so->ll.mtu) { dev_put(dev); err =3D -EINVAL; goto out; diff --git a/net/can/raw.c b/net/can/raw.c index 76b867d21def209f5c6d236604c0e434a1c55a4d..6cb959e3dcd3e54972628ee5957= 2a749009d1323 100644 --- a/net/can/raw.c +++ b/net/can/raw.c @@ -950,7 +950,7 @@ static int raw_sendmsg(struct socket *sock, struct msgh= dr *msg, size_t size) err =3D -EINVAL; =20 /* check for valid CAN (CC/FD/XL) frame content */ - txmtu =3D raw_check_txframe(ro, skb, dev->mtu); + txmtu =3D raw_check_txframe(ro, skb, READ_ONCE(dev->mtu)); if (!txmtu) goto free_skb; =20 --=20 2.49.1 From nobody Thu Oct 2 03:30:35 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E042E30FC06; Tue, 23 Sep 2025 06:37:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758609454; cv=none; b=ErMlLDnY7aPtwtF+HYxCK6g7TrOtTZr/7gLE1+JzPtqYfedtgZoLjZbVlLQtXzH5nPPqOV+L8MKYEisiEZv0eazlvIm90LDdrBGb7mQXnA9ZTq/6K+h0D8wLVkQBzV77j0twYrA0LXiU2FpyFm/dIyHF0O22JC4T0Thdn0e8o3w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758609454; c=relaxed/simple; bh=DneGXtD8h1Dl78Xv228aP26RFX4kDLuiIxklWvQi2F0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=bc7hiaNmQe88NDrnV9GRv7ci3226lNHEU8KOq4m1T4ntHJDwxBlSGro8pIZYr7c0sjnfuY0w/T55i34UCmhgZwL3eOssSeX1CIIEnOImPaK8F0vlDJ/rjIvajq90sdHvJHERomcBjr1bmvSs9gcLwhfIz6cp1ers1Yv9hX/tk48= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JtFkcKMp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JtFkcKMp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9140C116B1; Tue, 23 Sep 2025 06:37:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758609453; bh=DneGXtD8h1Dl78Xv228aP26RFX4kDLuiIxklWvQi2F0=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=JtFkcKMp371j+R6Q7m+c+mwBRYLuT/uIaXSOYSuiZUKCsjt07bjVv9/LSGzHwh8cM wFKUfrn5uz2bhWhyAJRn/Omy3PQkNAllQkl+DdF4WsyocwsFgovgTKKlfi51v/ImLB +sYI6gh20A94jsr37MGphMTDaOJ+8DFc63Dd0I6MyurlzDjITrfLfW9ncYLphVVzd2 n5+NgpfddlLxMw+PMflIm3o7N7+LHqYaB7MW2GX9sRtwhfy4JwX62eERVNeGg2wNIb R+Y+UDmrMU2NBoz+gSdw9WPYioxpjDUb3LypkbkJdK5W+Ekyu3JK5ViqX4Edvo0DkY r+aPKGpuFsK0g== From: Vincent Mailhol Date: Tue, 23 Sep 2025 15:37:09 +0900 Subject: [PATCH v3 2/4] can: dev: turn can_set_static_ctrlmode() into a non-inline function Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250923-can-fix-mtu-v3-2-581bde113f52@kernel.org> References: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> In-Reply-To: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> To: Oliver Hartkopp , Marc Kleine-Budde Cc: linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Mailhol X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3911; i=mailhol@kernel.org; h=from:subject:message-id; bh=DneGXtD8h1Dl78Xv228aP26RFX4kDLuiIxklWvQi2F0=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDBmXHBRXbgjVnBB3bYa52f6vpl58p05ceNP60aNh17m1p 56e+vniVUcpC4MYF4OsmCLLsnJOboWOQu+wQ38tYeawMoEMYeDiFICJGEgy/E/52Z5xe9bmOTum vpvG3SL7pig2YMbxlXVm5T85TZ/N0PZjZFi0Vf/45vj75gufP280ZdshnakVVB9lbvDRaMvXL1e OMnIBAA== X-Developer-Key: i=mailhol@kernel.org; a=openpgp; fpr=ED8F700574E67F20E574E8E2AB5FEB886DBB99C2 can_set_static_ctrlmode() is declared as a static inline. But it is only called in the probe function of the devices and so does not really benefit from any kind of optimization. Transform it into a "normal" function by moving it to drivers/net/can/dev/dev.c Signed-off-by: Vincent Mailhol --- This also serves as a preparation for the next patch in which we are adding can_set_default_mtu(). That function will only be used by the can_dev.ko module and so we do not need to export its GPL symbol. However, if can_set_static_ctrlmode() stays as a static inline, then the call to set_default_mtu(), which we plan to add in can_set_static_ctrlmode(), would also be inlined and thus would become visible to the users of can_set_static_ctrlmode(). Making can_set_static_ctrlmode() a non-inline function resolves this dependency. --- drivers/net/can/dev/dev.c | 21 +++++++++++++++++++++ include/linux/can/dev.h | 23 ++--------------------- 2 files changed, 23 insertions(+), 21 deletions(-) diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c index 3913971125de0ab16b4ad9f36712954141014ddf..a0ae659beedcd1fa0979662c126= 14ae7846032c0 100644 --- a/drivers/net/can/dev/dev.c +++ b/drivers/net/can/dev/dev.c @@ -347,6 +347,27 @@ int can_change_mtu(struct net_device *dev, int new_mtu) } EXPORT_SYMBOL_GPL(can_change_mtu); =20 +/* helper to define static CAN controller features at device creation time= */ +int can_set_static_ctrlmode(struct net_device *dev, u32 static_mode) +{ + struct can_priv *priv =3D netdev_priv(dev); + + /* alloc_candev() succeeded =3D> netdev_priv() is valid at this point */ + if (priv->ctrlmode_supported & static_mode) { + netdev_warn(dev, + "Controller features can not be supported and static at the same ti= me\n"); + return -EINVAL; + } + priv->ctrlmode =3D static_mode; + + /* override MTU which was set by default in can_setup()? */ + if (static_mode & CAN_CTRLMODE_FD) + dev->mtu =3D CANFD_MTU; + + return 0; +} +EXPORT_SYMBOL_GPL(can_set_static_ctrlmode); + /* generic implementation of netdev_ops::ndo_eth_ioctl for CAN devices * supporting hardware timestamps */ diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h index 9a92cbe5b2cb7ccdfca3121718856d096e9ecfa6..5dc58360c2d74a1711d4e02d28f= e52ae20b146e0 100644 --- a/include/linux/can/dev.h +++ b/include/linux/can/dev.h @@ -125,27 +125,6 @@ static inline s32 can_get_relative_tdco(const struct c= an_priv *priv) return (s32)priv->fd.tdc.tdco - sample_point_in_tc; } =20 -/* helper to define static CAN controller features at device creation time= */ -static inline int __must_check can_set_static_ctrlmode(struct net_device *= dev, - u32 static_mode) -{ - struct can_priv *priv =3D netdev_priv(dev); - - /* alloc_candev() succeeded =3D> netdev_priv() is valid at this point */ - if (priv->ctrlmode_supported & static_mode) { - netdev_warn(dev, - "Controller features can not be supported and static at the same ti= me\n"); - return -EINVAL; - } - priv->ctrlmode =3D static_mode; - - /* override MTU which was set by default in can_setup()? */ - if (static_mode & CAN_CTRLMODE_FD) - dev->mtu =3D CANFD_MTU; - - return 0; -} - static inline u32 can_get_static_ctrlmode(struct can_priv *priv) { return priv->ctrlmode & ~priv->ctrlmode_supported; @@ -188,6 +167,8 @@ struct can_priv *safe_candev_priv(struct net_device *de= v); int open_candev(struct net_device *dev); void close_candev(struct net_device *dev); int can_change_mtu(struct net_device *dev, int new_mtu); +int __must_check can_set_static_ctrlmode(struct net_device *dev, + u32 static_mode); int can_eth_ioctl_hwts(struct net_device *netdev, struct ifreq *ifr, int c= md); int can_ethtool_op_get_ts_info_hwts(struct net_device *dev, struct kernel_ethtool_ts_info *info); --=20 2.49.1 From nobody Thu Oct 2 03:30:35 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 04C2630FC31; Tue, 23 Sep 2025 06:37:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758609455; cv=none; b=YCLnx/9pa4MiH3buQaaUq4kw4u7yt0q0D53vyKVwIw8sleY9SbsAaFWRGQ1+nkDE02UIqGlToslrv697y8i03Do5J1I9w9r1AwM2BcM8WS3RsdNUh/QcgEfBt9BrFx/sKvlmrHc4ZxGSl2U80UtpDiIqhctO/hv65u2WVZUjycw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758609455; c=relaxed/simple; bh=Zj00qJ2G6wtMCMGxh6W71gJtBiAdkMplYJcXlpTDfLk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ujZQj6AfP65kd/j/vY1AC5aGhaXHle8Z7eOzpc3VZTO7cxc1kos3wSaApJRMQYf4XycSL7LkFKCNItP0EHPx51dJjZP4j+1zXM9eCiUAtrZlXuwGUE7FK+Ns4cjb6jzFXuMwocriAw+lPhU/IDeqLz/BA+VWd/Lgm9qse7coGOg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=n8b+MyuS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="n8b+MyuS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6EACC116C6; Tue, 23 Sep 2025 06:37:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758609454; bh=Zj00qJ2G6wtMCMGxh6W71gJtBiAdkMplYJcXlpTDfLk=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=n8b+MyuS6imcQOdMqgNNuhsbO4ZAbypL849gCYMzQ1hE8OqmGxXNYQvkzCqUGuikS N9tayWi1P6/CEDKcqrInjB5DYR+fdxHhcR9r6WQ4l5s1cn8RnKNJfK2NGpR1hn8juP pgYiAl76sseJi8n0y02VPCA2j5hO6R9qu+P45LCQESCcjERaHvj+QveFVXdRtdBSY3 pwX89xmLvlJSpQTG6Cyjicitu2FgMzKBslq6TWUvdYCniHF/rZESFuGQ2WWTYcTeg3 u/EQiliBu5JY57ReShiX52yuzchrbQqXbbKrSey/RZLNsQ/uhuT/iAteYXtvnRAlmX QBC4wizU6i6yQ== From: Vincent Mailhol Date: Tue, 23 Sep 2025 15:37:10 +0900 Subject: [PATCH v3 3/4] can: populate the minimum and maximum MTU values Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250923-can-fix-mtu-v3-3-581bde113f52@kernel.org> References: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> In-Reply-To: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> To: Oliver Hartkopp , Marc Kleine-Budde Cc: linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Mailhol X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=5119; i=mailhol@kernel.org; h=from:subject:message-id; bh=Zj00qJ2G6wtMCMGxh6W71gJtBiAdkMplYJcXlpTDfLk=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDBmXHFR4v/psVUjasIOZfZfXp2JuK8UCnczjc39997927 0L0rA26HaUsDGJcDLJiiizLyjm5FToKvcMO/bWEmcPKBDKEgYtTACYy6Sojw6tns5K3dvLu2H32 9uF/DJ8eHNHRYLG6EaabxDR54ndLASOG/0nrFt8z7nZ8slKEq1b5wvn5icZzT/bqNS6bKmF0/nK HJBMA X-Developer-Key: i=mailhol@kernel.org; a=openpgp; fpr=ED8F700574E67F20E574E8E2AB5FEB886DBB99C2 By populating: net_device->min_mtu and net_device->max_mtu the net core infrastructure will automatically: 1. validate that the user's inputs are in range. 2. report those min and max MTU values through the netlink interface. Add can_set_default_mtu() which sets the default mtu value as well as the minimum and maximum values. The logic for the default mtu value remains unchanged: - CANFD_MTU if the device has a static CAN_CTRLMODE_FD. - CAN_MTU otherwise. Call can_set_default_mtu() each time the CAN_CTRLMODE_FD is modified. This will guarantee that the MTU value is always consistent with the control mode flags. With this, the checks done in can_change_mtu() become fully redundant and will be removed in an upcoming change and it is now possible to confirm the minimum and maximum MTU values on a physical CAN interface by doing: $ ip --details link show can0 The virtual interfaces (vcan and vxcan) are not impacted by this change. Signed-off-by: Vincent Mailhol --- With this, when adding the CAN XL netlink interface, all we have to do is to add one if branch to can_set_default_mtu() like this: void can_set_default_mtu(struct net_device *dev) { struct can_priv *priv =3D netdev_priv(dev); if (priv->ctrlmode & CAN_CTRLMODE_XL) { if (can_is_canxl_dev_mtu(dev->mtu)) return; dev->mtu =3D CANXL_MTU; dev->min_mtu =3D CANXL_MIN_MTU; dev->max_mtu =3D CANXL_MAX_MTU; } else if (priv->ctrlmode & CAN_CTRLMODE_FD) { dev->mtu =3D CANFD_MTU; dev->min_mtu =3D CANFD_MTU; dev->max_mtu =3D CANFD_MTU; } else { dev->mtu =3D CAN_MTU; dev->min_mtu =3D CAN_MTU; dev->max_mtu =3D CAN_MTU; } } and we will be done! --- drivers/net/can/dev/dev.c | 21 ++++++++++++++++++--- drivers/net/can/dev/netlink.c | 9 ++++----- include/linux/can/dev.h | 1 + 3 files changed, 23 insertions(+), 8 deletions(-) diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c index a0ae659beedcd1fa0979662c12614ae7846032c0..69c00720e9956cad986ea86fbba= 49285d76f51db 100644 --- a/drivers/net/can/dev/dev.c +++ b/drivers/net/can/dev/dev.c @@ -239,11 +239,12 @@ EXPORT_SYMBOL_GPL(can_bus_off); void can_setup(struct net_device *dev) { dev->type =3D ARPHRD_CAN; - dev->mtu =3D CAN_MTU; dev->hard_header_len =3D 0; dev->addr_len =3D 0; dev->tx_queue_len =3D 10; =20 + can_set_default_mtu(dev); + /* New-style flags. */ dev->flags =3D IFF_NOARP; dev->features =3D NETIF_F_HW_CSUM; @@ -309,6 +310,21 @@ void free_candev(struct net_device *dev) } EXPORT_SYMBOL_GPL(free_candev); =20 +void can_set_default_mtu(struct net_device *dev) +{ + struct can_priv *priv =3D netdev_priv(dev); + + if (priv->ctrlmode & CAN_CTRLMODE_FD) { + dev->mtu =3D CANFD_MTU; + dev->min_mtu =3D CANFD_MTU; + dev->max_mtu =3D CANFD_MTU; + } else { + dev->mtu =3D CAN_MTU; + dev->min_mtu =3D CAN_MTU; + dev->max_mtu =3D CAN_MTU; + } +} + /* changing MTU and control mode for CAN/CANFD devices */ int can_change_mtu(struct net_device *dev, int new_mtu) { @@ -361,8 +377,7 @@ int can_set_static_ctrlmode(struct net_device *dev, u32= static_mode) priv->ctrlmode =3D static_mode; =20 /* override MTU which was set by default in can_setup()? */ - if (static_mode & CAN_CTRLMODE_FD) - dev->mtu =3D CANFD_MTU; + can_set_default_mtu(dev); =20 return 0; } diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c index d9f6ab3efb9767409c318b714f19df8a30e51137..248f607e3864ffbda6f0b8daf4e= 2484179cf9cd5 100644 --- a/drivers/net/can/dev/netlink.c +++ b/drivers/net/can/dev/netlink.c @@ -223,17 +223,16 @@ static int can_changelink(struct net_device *dev, str= uct nlattr *tb[], priv->ctrlmode &=3D ~cm->mask; priv->ctrlmode |=3D maskedflags; =20 - /* CAN_CTRLMODE_FD can only be set when driver supports FD */ - if (priv->ctrlmode & CAN_CTRLMODE_FD) { - dev->mtu =3D CANFD_MTU; - } else { - dev->mtu =3D CAN_MTU; + /* Wipe potential leftovers from previous CAN FD config */ + if (!(priv->ctrlmode & CAN_CTRLMODE_FD)) { memset(&priv->fd.data_bittiming, 0, sizeof(priv->fd.data_bittiming)); priv->ctrlmode &=3D ~CAN_CTRLMODE_FD_TDC_MASK; memset(&priv->fd.tdc, 0, sizeof(priv->fd.tdc)); } =20 + can_set_default_mtu(dev); + fd_tdc_flag_provided =3D cm->mask & CAN_CTRLMODE_FD_TDC_MASK; /* CAN_CTRLMODE_TDC_{AUTO,MANUAL} are mutually * exclusive: make sure to turn the other one off diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h index 5dc58360c2d74a1711d4e02d28fe52ae20b146e0..3354f70ed2c684d7d482549560d= 4cb5838cbebd5 100644 --- a/include/linux/can/dev.h +++ b/include/linux/can/dev.h @@ -166,6 +166,7 @@ struct can_priv *safe_candev_priv(struct net_device *de= v); =20 int open_candev(struct net_device *dev); void close_candev(struct net_device *dev); +void can_set_default_mtu(struct net_device *dev); int can_change_mtu(struct net_device *dev, int new_mtu); int __must_check can_set_static_ctrlmode(struct net_device *dev, u32 static_mode); --=20 2.49.1 From nobody Thu Oct 2 03:30:35 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1C5ED30FF2B; Tue, 23 Sep 2025 06:37:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758609456; cv=none; b=B5AiGC0oxGsqsRP/LpSfI6mLi9R7C6WjXNXzD6QsV3bcfCA7lznlEgG7zNKin393zPatmjfX69eUYE78QiPkomqcSGokjabYe/82JjPG/0JzuZs8ddtrZepU4mzdnBzzsldGAVdMH/0aRTg0z6jv1FLNVLdsDfeQ/+QvLIHsOOE= ARC-Message-Signature: i=1; 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b=Yid5DSO5OInIoJg8c9aESz7+ekB6vofo7fonrI+I7fzXnN5onXi7XeUnzViH4/uCc baTxLuTMHGdUIE4vOI+cfFJKq0wALaMurKR/UOEVQDZerwmOKG3uSUXXfpdY+Lb9RG iq+KsdOAWwbF2vP4BbSOlcige3sJGzR+VQrHn+tzK2A+admGFRtgGESJv3XajEe7QG D4whkSb3ZbTmiU56+cme1J74jwynYetwFb4BwDwcgHAFlt5wbEMQrKNLzwEO6J4ug0 snol8yrlEZ6qQCxS8t4uAo1GU/8QifQPAmVZSMinifCk3ySrzqzNiC40k4MwOo75pF e8QC9jilLQU/w== From: Vincent Mailhol Date: Tue, 23 Sep 2025 15:37:11 +0900 Subject: [PATCH v3 4/4] can: enable CAN XL for virtual CAN devices by default Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250923-can-fix-mtu-v3-4-581bde113f52@kernel.org> References: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> In-Reply-To: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> To: Oliver Hartkopp , Marc Kleine-Budde Cc: linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Mailhol X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1737; i=mailhol@kernel.org; h=from:subject:message-id; bh=2/MlNtQVs67BhcBQu3mBYH5/+H7qem0YfGtT2lPXmQw=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDBmXHNQvBBd7FG6ZOu/poX87d5YcO2nRpcN9if/x/dPp6 duaFxuwd5SyMIhxMciKKbIsK+fkVugo9A479NcSZg4rE8gQBi5OAZhI305GhqOczpdXc7esDbjW 23r6N3Pi9iOcZzfEFLwoetHi/+bQimOMDO9nHNgiEz7H7E/NvtwDZsmP5y+sLlt8dRnHlNc+a5r 2mvECAA== X-Developer-Key: i=mailhol@kernel.org; a=openpgp; fpr=ED8F700574E67F20E574E8E2AB5FEB886DBB99C2 In commit 97edec3a11cf ("can: enable CAN FD for virtual CAN devices by default"), vcan and vxcan default MTU was set to CANFD_MTU by default. The reason was that users were confused on how to activate CAN FD on virtual interfaces. Following the introduction of CAN XL, the same logic should be applied. Set the MTU to CANXL_MTU by default. The users who really wish to use a Classical CAN only or a CAN FD virtual device can do respectively: $ ip link set vcan0 mtu 16 or $ ip link set vcan0 mtu 72 to force the old behaviour. Signed-off-by: Vincent Mailhol --- drivers/net/can/vcan.c | 2 +- drivers/net/can/vxcan.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/can/vcan.c b/drivers/net/can/vcan.c index f67e858071007acd5f34fa00a76212f1a77997a6..fdc662aea2798125b3aa373f099= 58363b427ced2 100644 --- a/drivers/net/can/vcan.c +++ b/drivers/net/can/vcan.c @@ -156,7 +156,7 @@ static const struct ethtool_ops vcan_ethtool_ops =3D { static void vcan_setup(struct net_device *dev) { dev->type =3D ARPHRD_CAN; - dev->mtu =3D CANFD_MTU; + dev->mtu =3D CANXL_MTU; dev->hard_header_len =3D 0; dev->addr_len =3D 0; dev->tx_queue_len =3D 0; diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c index 99a78a75716749bf858cc78eadb41ca2588fcf94..b2c19f8c5f8e5101b8be343401a= fe9a4f388c4da 100644 --- a/drivers/net/can/vxcan.c +++ b/drivers/net/can/vxcan.c @@ -156,7 +156,7 @@ static void vxcan_setup(struct net_device *dev) struct can_ml_priv *can_ml; =20 dev->type =3D ARPHRD_CAN; - dev->mtu =3D CANFD_MTU; + dev->mtu =3D CANXL_MTU; dev->hard_header_len =3D 0; dev->addr_len =3D 0; dev->tx_queue_len =3D 0; --=20 2.49.1