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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED 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 516F7C43219 for ; Thu, 2 May 2019 07:56:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 199432085A for ; Thu, 2 May 2019 07:56:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="K1azEk9F" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726276AbfEBH4p (ORCPT ); Thu, 2 May 2019 03:56:45 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:42244 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725795AbfEBH4p (ORCPT ); Thu, 2 May 2019 03:56:45 -0400 Received: by mail-qt1-f194.google.com with SMTP id p20so1416673qtc.9 for ; Thu, 02 May 2019 00:56:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=oRQNrBl3LbUWqyjxjhcKLS8Zdkaq+AHCYKUjrU7AoLE=; b=K1azEk9FUZTF8l2OPl9v0vSzvaDSDakovrJzRcwbtRPQ1Ki/rEsvk6No2vUF4HY1+J GOXHNzqdPU489+RSuELiGvWh09jiS0XtJErSFv0tSB+JV30b3XP21kZbXLPo62tuy8z3 wXmBOqchvpNA6BfRQ/EbaK+Bmh9YPtfYK+Un0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=oRQNrBl3LbUWqyjxjhcKLS8Zdkaq+AHCYKUjrU7AoLE=; b=UpUAPf/upSvWNRuXQ1aAPzmjhoc95l759p/NPkGXnhs6k7cY2N9wL6JkhVcSWtPLMJ y0Y1ID7A7Ji0GUWYmMBYri2nFsjookzAwtOUHjNHmfaT6/cwSpNmo8jBd9mNxniikHxs qLwkCLMcrj8S0ZT4QV9nr5R2RwbAzErN2UeX0SDHvd34BD5AiQ33gKvLzK4rbmj2/E4S bHpjp9hmgVxx2+zctpsqStfwTr0qROTmtpMzxD9uqVyLsNdHgiSP5uxoNN+y3muheQU+ L5vaYzS2ykt944Netz3cr6oJa4+MRKbeosOp/7l50OR5plbWH3wilNkKro5b2n6vIVZf p4mQ== X-Gm-Message-State: APjAAAX4CPfoU/3FjqbshfUQIGT4P7LuCPepiILx8cerG0X8mvl2BMIR IBXg/qZ1F0DNIkxha3FcdHhYtXLXafNv56jzOvgBNQ== X-Google-Smtp-Source: APXvYqwM6qmZs9QMprvFC8eT7hNgb431bDfnqEf3Whh9ByrBUw3+WOxYgsMMm0S/s1eXLuhWM/HhUi2jlX8+QcMgJeE= X-Received: by 2002:ac8:362e:: with SMTP id m43mr1985816qtb.339.1556783804389; Thu, 02 May 2019 00:56:44 -0700 (PDT) MIME-Version: 1.0 References: <20190418075016.252988-1-pihsun@chromium.org> In-Reply-To: <20190418075016.252988-1-pihsun@chromium.org> From: Nicolas Boichat Date: Thu, 2 May 2019 15:56:33 +0800 Message-ID: Subject: Re: [PATCH] wireless: Use offsetof instead of custom macro. To: Pi-Hsun Shih Cc: open list Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 18, 2019 at 3:50 PM Pi-Hsun Shih wrote: > > Use offsetof to calculate offset of a field to take advantage of > compiler built-in version when possible, and avoid UBSAN warning when > compiling with Clang: > > ================================================================== > UBSAN: Undefined behaviour in net/wireless/wext-core.c:525:14 > member access within null pointer of type 'struct iw_point' > CPU: 3 PID: 165 Comm: kworker/u16:3 Tainted: G S W 4.19.23 #43 > Workqueue: cfg80211 __cfg80211_scan_done [cfg80211] > Call trace: > dump_backtrace+0x0/0x194 > show_stack+0x20/0x2c > __dump_stack+0x20/0x28 > dump_stack+0x70/0x94 > ubsan_epilogue+0x14/0x44 > ubsan_type_mismatch_common+0xf4/0xfc > __ubsan_handle_type_mismatch_v1+0x34/0x54 > wireless_send_event+0x3cc/0x470 > ___cfg80211_scan_done+0x13c/0x220 [cfg80211] > __cfg80211_scan_done+0x28/0x34 [cfg80211] > process_one_work+0x170/0x35c > worker_thread+0x254/0x380 > kthread+0x13c/0x158 > ret_from_fork+0x10/0x18 > =================================================================== > > Signed-off-by: Pi-Hsun Shih The warning from clang is spurious, but in another case, we felt that the cleanup was worth it, nevertheless (https://lore.kernel.org/patchwork/patch/1050040/). Reviewed-By: Nicolas Boichat > --- > include/uapi/linux/wireless.h | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/include/uapi/linux/wireless.h b/include/uapi/linux/wireless.h > index 86eca3208b6b..f259cca5cc2b 100644 > --- a/include/uapi/linux/wireless.h > +++ b/include/uapi/linux/wireless.h > @@ -1090,8 +1090,7 @@ struct iw_event { > /* iw_point events are special. First, the payload (extra data) come at > * the end of the event, so they are bigger than IW_EV_POINT_LEN. Second, > * we omit the pointer, so start at an offset. */ > -#define IW_EV_POINT_OFF (((char *) &(((struct iw_point *) NULL)->length)) - \ > - (char *) NULL) > +#define IW_EV_POINT_OFF offsetof(struct iw_point, length) > #define IW_EV_POINT_LEN (IW_EV_LCP_LEN + sizeof(struct iw_point) - \ > IW_EV_POINT_OFF) > > -- > 2.21.0.392.gf8f6787159e-goog >