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=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 03C36C433E0 for ; Tue, 2 Feb 2021 10:10:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B052664F54 for ; Tue, 2 Feb 2021 10:10:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229902AbhBBKKE (ORCPT ); Tue, 2 Feb 2021 05:10:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229534AbhBBKJy (ORCPT ); Tue, 2 Feb 2021 05:09:54 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82746C061573 for ; Tue, 2 Feb 2021 02:09:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Ab16otijG9bvAhz8VfD19hPIsyJecqtgK3hKzle+tDo=; b=cYlNH1xtktfv50ymA4Pp8pOdSN gtu1upXQtK08hAxSW0sFfy7aaUEVnjs3I2Rn2tfGMRIMaaV/djL7Bwz8IomO133jPuTlic+JSKhzv fvjUOTxYsr7I1ziASa7gu4jySLAJ7XwQVISw05mpzC3QVJ2l6ppoHSEfTxLW79muMKM7aTmDlRZ90 dC0ICajuvQlTCyS+Zc/oln4H6LKI/gURQi2mRDKYWJ3vNAu8GJq53zjQiTLQIxpk09+k9EIwtBim6 URi5judJ9OJX/8A5HaQn90bfPy3T3IL0FpZOKZXQiBK1NdI8UvOly/FwcZjlkJRfOuAduCe76AD0I icrAJkMQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1l6scC-0006Dk-Rz; Tue, 02 Feb 2021 10:08:57 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 01405301A66; Tue, 2 Feb 2021 11:08:54 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BA3DA299C9F60; Tue, 2 Feb 2021 11:08:54 +0100 (CET) Date: Tue, 2 Feb 2021 11:08:54 +0100 From: Peter Zijlstra To: Alexey Kardashevskiy Cc: Steven Rostedt , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Ingo Molnar , John Fastabend , KP Singh , Martin KaFai Lau , Song Liu , Yonghong Song , linux-kernel@vger.kernel.org Subject: Re: [PATCH kernel] tracepoint: Fix race between tracing and removing tracepoint Message-ID: References: <20210202072326.120557-1-aik@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210202072326.120557-1-aik@ozlabs.ru> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 02, 2021 at 06:23:26PM +1100, Alexey Kardashevskiy wrote: > When executing a tracepoint, the tracepoint's func is dereferenced twice - > in __DO_TRACE() (where the returned pointer is checked) and later on in > __traceiter_##_name where the returned pointer is dereferenced without > checking which leads to races against tracepoint_removal_sync() and > crashes. > > This adds a check before referencing the pointer in tracepoint_ptr_deref. Agreed, a reload got added and it doesn't check the value again. > Fixes: d25e37d89dd2f ("tracepoint: Optimize using static_call()") > Signed-off-by: Alexey Kardashevskiy > it_func_ptr = \ > rcu_dereference_raw((&__tracepoint_##_name)->funcs); \ > + if (it_func_ptr) { \ > + do { \ > + it_func = (it_func_ptr)->func; \ > + __data = (it_func_ptr)->data; \ > + ((void(*)(void *, proto))(it_func))(__data, args); \ > + } while ((++it_func_ptr)->func); \ > + } \ > return 0; \ Acked-by: Peter Zijlstra (Intel)