From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from metis.whiteo.stw.pengutronix.de (metis.whiteo.stw.pengutronix.de [185.203.201.7]) (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 67516288C08 for ; Mon, 20 Apr 2026 12:18:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.203.201.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776687519; cv=none; b=YW0ai2umsvI3qRb02T40pm/8Qdm8MZdytTV/Q/5bVxrIHNH3PHGtWwdWJgkx3/MTtKwhsb9yQ7kxtQde2fDnDVZxbTH+w+hmrnBDXrreDLWQVvv7P2Q+C1WELLiM2WyDVoivaVl02YND7bSMl6Bz04nTw9GMD3fvs0JvBzBSFUA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776687519; c=relaxed/simple; bh=iKdh0huWgoYjFm0DOT34aRCgqoK921FtqaFHufRQvDY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kVJNUMIhGZl5s6J56DW9dmGzQA4m5gkiJwPqoOP3Tn3C/t0HH8LzrxjtoZFlgYju7bX/q9vqr5Rkv7StN1ASvMzgtbR1IKkpWxBEKgBW/C/Lq8d2cuxUwLJv0aD1t+SmSnl3YdRkC6zZPV8suY8FoIioj3TYfhnlfUUYrOCyA+A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de; spf=pass smtp.mailfrom=pengutronix.de; arc=none smtp.client-ip=185.203.201.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pengutronix.de Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1wEna1-0004pw-Hl; Mon, 20 Apr 2026 14:18:21 +0200 Received: from pty.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::c5]) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1wEnZz-006Kk1-2U; Mon, 20 Apr 2026 14:18:19 +0200 Received: from ore by pty.whiteo.stw.pengutronix.de with local (Exim 4.98.2) (envelope-from ) id 1wEnZz-00000004GUf-2lGs; Mon, 20 Apr 2026 14:18:19 +0200 Date: Mon, 20 Apr 2026 14:18:19 +0200 From: Oleksij Rempel To: Shuhao Fu Cc: Robin van der Gracht , linux-can@vger.kernel.org, kernel@pengutronix.de, Oliver Hartkopp , Marc Kleine-Budde , linux-kernel@vger.kernel.org Subject: Re: [PATCH net] can: j1939: fix lockless local-destination check Message-ID: References: <20260419140614.GA4041240@chcpu16> 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-Disposition: inline In-Reply-To: <20260419140614.GA4041240@chcpu16> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Hi, On Sun, Apr 19, 2026 at 10:06:14PM +0800, Shuhao Fu wrote: > j1939_priv.ents[].nusers is documented as protected by priv->lock, and > its updates already happen under that lock. j1939_can_recv() also reads > it under read_lock_bh(). However, j1939_session_skb_queue() and > j1939_tp_send() still read priv->ents[da].nusers without taking the > lock. > > Those transport-side checks decide whether to set J1939_ECU_LOCAL_DST, so > they can race with j1939_local_ecu_get() and j1939_local_ecu_put() while > userspace is binding or releasing sockets concurrently with TP traffic. > This can misclassify TP/ETP sessions as local or remote and take the wrong > transport path. > > Fix both transport paths by routing the destination-locality check through > a helper that reads ents[].nusers under read_lock_bh(&priv->lock). > > Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > Signed-off-by: Shuhao Fu Thank you for your work. LGTM. Tested-by: Oleksij Rempel Acked-by: Oleksij Rempel -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |