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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA3EDC4332F for ; Fri, 16 Dec 2022 20:32:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229506AbiLPUc5 (ORCPT ); Fri, 16 Dec 2022 15:32:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38538 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229568AbiLPUcz (ORCPT ); Fri, 16 Dec 2022 15:32:55 -0500 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E1AA3FAF8 for ; Fri, 16 Dec 2022 12:32:54 -0800 (PST) Received: by mail-pl1-x632.google.com with SMTP id n4so3455411plp.1 for ; Fri, 16 Dec 2022 12:32:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=ZHhZ9ZPwjqbZ4BcttSt3Sdnf2qIn3B52gMX2PCgd3xg=; b=LWJb4jETCkdIV7xwZtPKFKqnBfRSGtDxr7b66C7yE2bTbTaDzkWz+4OKI39o84LAKl 0K8UgyhKz8UI++gjYxjpZc42BOykIlvpCB0rQYhwh8+TMTFNEpLpjcKujq9JGiROE6s5 jTPkLUp4wlnBaeM32SbGfc66gmPSy63uURfoY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=ZHhZ9ZPwjqbZ4BcttSt3Sdnf2qIn3B52gMX2PCgd3xg=; b=siVmXZ6sbZ/R6mIkNh0+w7gUO/u3Yz6w9CfUcmzgz+hP1XgFwf4h511G5eSBY/Milx wRbjQb/uNGxkB/RgeshimAo/gChLjj+MJ0u0uH0RXKiAv+31/5cyUC1nL8EyQXRDIykU tYiiDf9/sTg2Jg+eYczoQajYY6OzAN0fdRm8q/QRQBbKeVVsYNnIb2jL1kBknkyw/qYL cCU4SOUdFjadbHNgQi8EbwRvGM8DdheO/0jJx5GgmKTFuBCqjYuJPNQy4WRCtxcFGdfJ Gi2vzF9sOBoetRoXu7JiL2QeHk6gZfB6TIP691rnROK6i8dpQpg4KSRycpbcCxNZzmDM N5yg== X-Gm-Message-State: ANoB5pnOtNtLxvROBV+v0jIDcAtwbQxyJzsq2ah8WzzemK8QFJEWr/G+ Cp09dMqJs4Bw8B69aHWPLswzzg== X-Google-Smtp-Source: AA0mqf6Y2ZywjGs0mB+Uova/fqMsnSnunDEP+ZiLAHwTDeXSyAzc/Cvzm2FmPHyyWH35eIUM0u3IWA== X-Received: by 2002:a17:902:ab8d:b0:187:467f:c76c with SMTP id f13-20020a170902ab8d00b00187467fc76cmr30243669plr.51.1671222774412; Fri, 16 Dec 2022 12:32:54 -0800 (PST) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id v7-20020a170902b7c700b00186e2123506sm2005977plz.300.2022.12.16.12.32.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Dec 2022 12:32:53 -0800 (PST) Date: Fri, 16 Dec 2022 12:32:53 -0800 From: Kees Cook To: Peter Zijlstra Cc: Jann Horn , Seth Jenkins , Jonathan Corbet , Andrew Morton , Baolin Wang , "Jason A. Donenfeld" , Eric Biggers , Huang Ying , "Eric W. Biederman" , Arnd Bergmann , linux-doc@vger.kernel.org, "Guilherme G. Piccoli" , Joel Savitz , Laurent Dufour , Rob Herring , Al Viro , Ingo Molnar , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] exit: Allow oops_limit to be disabled Message-ID: <202212161232.D752E46@keescook> References: <20221202210617.never.105-kees@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, Dec 16, 2022 at 03:05:13PM +0100, Peter Zijlstra wrote: > On Fri, Dec 02, 2022 at 01:06:21PM -0800, Kees Cook wrote: > > > --- a/kernel/exit.c > > +++ b/kernel/exit.c > > @@ -954,7 +954,7 @@ void __noreturn make_task_dead(int signr) > > * To make sure this can't happen, place an upper bound on how often the > > * kernel may oops without panic(). > > */ > > - if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit)) > > + if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit) && oops_limit) > > panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit); > > > > That's dodgy, please write as: > > limit = READ_ONCE(oops_limit); > if (atomic_inc_return(&oops_count) >= limit && limit) > > So we don't explicitly add a reload that negates the whole READ_ONCE(). Yup, that's more correct. Sent: https://lore.kernel.org/lkml/20221216203024.never.640-kees@kernel.org -- Kees Cook