From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22946C43470 for ; Mon, 12 Apr 2021 09:12:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E9BC76120F for ; Mon, 12 Apr 2021 09:12:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239602AbhDLJNK (ORCPT ); Mon, 12 Apr 2021 05:13:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:35848 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240254AbhDLJKK (ORCPT ); Mon, 12 Apr 2021 05:10:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id B018F6128E; Mon, 12 Apr 2021 09:04:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1618218299; bh=CSI6dbRTe9p+rwMBbEBSxBmGC506+71RrdXacmKp01o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EtzgUNjjRRTi0sB1uLgrpAz81sXtReGr9SmNNbIGgjK9uKJGGtp7ReKcqBd1vvTqk manLBa9/lfqVyit4C3jorTYLYQ5sBq77rDjIMQmO+OPGQy1tm9iEZCQAGI8DXt6Ctn eFwqAhYET66Vlt3NValjKZV5nkSD5UOKlT2p33Lw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, kernel test robot , Rong Chen , Oliver Hartkopp , Marc Kleine-Budde , Sasha Levin Subject: [PATCH 5.11 128/210] can: uapi: can.h: mark union inside struct can_frame packed Date: Mon, 12 Apr 2021 10:40:33 +0200 Message-Id: <20210412084020.280059263@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210412084016.009884719@linuxfoundation.org> References: <20210412084016.009884719@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Marc Kleine-Budde [ Upstream commit f5076c6ba02e8e24c61c40bbf48078929bc0fc79 ] In commit ea7800565a12 ("can: add optional DLC element to Classical CAN frame structure") the struct can_frame::can_dlc was put into an anonymous union with another u8 variable. For various reasons some members in struct can_frame and canfd_frame including the first 8 byes of data are expected to have the same memory layout. This is enforced by a BUILD_BUG_ON check in af_can.c. Since the above mentioned commit this check fails on ARM kernels compiled with the ARM OABI (which means CONFIG_AEABI not set). In this case -mabi=apcs-gnu is passed to the compiler, which leads to a structure size boundary of 32, instead of 8 compared to CONFIG_AEABI enabled. This means the the union in struct can_frame takes 4 bytes instead of the expected 1. Rong Chen illustrates the problem with pahole in the ARM OABI case: | struct can_frame { | canid_t can_id; /* 0 4 */ | union { | __u8 len; /* 4 1 */ | __u8 can_dlc; /* 4 1 */ | }; /* 4 4 */ | __u8 __pad; /* 8 1 */ | __u8 __res0; /* 9 1 */ | __u8 len8_dlc; /* 10 1 */ | | /* XXX 5 bytes hole, try to pack */ | | __u8 data[8] | __attribute__((__aligned__(8))); /* 16 8 */ | | /* size: 24, cachelines: 1, members: 6 */ | /* sum members: 19, holes: 1, sum holes: 5 */ | /* forced alignments: 1, forced holes: 1, sum forced holes: 5 */ | /* last cacheline: 24 bytes */ | } __attribute__((__aligned__(8))); Marking the anonymous union as __attribute__((packed)) fixes the BUILD_BUG_ON problem on these compilers. Fixes: ea7800565a12 ("can: add optional DLC element to Classical CAN frame structure") Reported-by: kernel test robot Suggested-by: Rong Chen Link: https://lore.kernel.org/linux-can/2c82ec23-3551-61b5-1bd8-178c3407ee83@hartkopp.net/ Link: https://lore.kernel.org/r/20210325125850.1620-3-socketcan@hartkopp.net Signed-off-by: Oliver Hartkopp Signed-off-by: Marc Kleine-Budde Signed-off-by: Sasha Levin --- include/uapi/linux/can.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/uapi/linux/can.h b/include/uapi/linux/can.h index f75238ac6dce..c7535352fef6 100644 --- a/include/uapi/linux/can.h +++ b/include/uapi/linux/can.h @@ -113,7 +113,7 @@ struct can_frame { */ __u8 len; __u8 can_dlc; /* deprecated */ - }; + } __attribute__((packed)); /* disable padding added in some ABIs */ __u8 __pad; /* padding */ __u8 __res0; /* reserved / padding */ __u8 len8_dlc; /* optional DLC for 8 byte payload length (9 .. 15) */ -- 2.30.2