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=-1.0 required=3.0 tests=MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 5016FC433E0 for ; Thu, 18 Jun 2020 00:01:58 +0000 (UTC) Received: from krantz.zx2c4.com (krantz.zx2c4.com [192.95.5.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 03C9221556 for ; Thu, 18 Jun 2020 00:01:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 03C9221556 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=wireguard-bounces@lists.zx2c4.com Received: by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 3aa1613c; Wed, 17 Jun 2020 23:43:21 +0000 (UTC) Received: from mail-ed1-f66.google.com (mail-ed1-f66.google.com [209.85.208.66]) by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTPS id cc80d6cc (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO) for ; Wed, 17 Jun 2020 23:43:19 +0000 (UTC) Received: by mail-ed1-f66.google.com with SMTP id e12so3502219eds.2 for ; Wed, 17 Jun 2020 17:01:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=fOVgSeVqTVqWvUfLoOdj4nt+48hh42lucWZp1VWswtg=; b=QiH1qanAk1UoASb26wgiYDc6PgbquwJDSS7vpcO8iCHSAKeICldVa2xatWNj2F/v/M roJ0vmRMMeL1izBQBGJhoV7aae3SBtPR8PKCLK1E059o7fZce1oQmM/lB0mST7Sxpb7x jnbIYY7fWTOu+ZGJbiKz1jdAolyD5fs02fIZ461YPWx8pY7RRvzp8kwVYBOI0aiPafey Geu7tp6FslwCuBAHJiIhr9H85ZoJw7Da8BJiZGf6wXIU0CHVyG1RklqVRvg2cVpiuGvS 88wkBkXfjaNE47XVqn2CqrdMBSg2dY45epwdZ4g6JJI340Q4EeRszplf4ee1ud1Ku6vK ZUzw== X-Gm-Message-State: AOAM532HhX2EvuWYbsma1jFwbQLtjZEvpBiC/IgI2GRs7eRUUPtpg/5v AFO1PWYOFl09loBMXaF43/F2RUJmfV4= X-Google-Smtp-Source: ABdhPJz5smjYQcDGdXsq8Ug+fgHwHPeIMnfqM9kX0E57nHrzErZZpyVOrifVPC/iAZURBZCGoIl/9Q== X-Received: by 2002:a17:906:aad8:: with SMTP id kt24mr7265073ejb.527.1592398555771; Wed, 17 Jun 2020 05:55:55 -0700 (PDT) Received: from localhost (ip-37-188-158-19.eurotel.cz. [37.188.158.19]) by smtp.gmail.com with ESMTPSA id mh14sm13501385ejb.116.2020.06.17.05.55.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Jun 2020 05:55:54 -0700 (PDT) Date: Wed, 17 Jun 2020 14:55:53 +0200 From: Michal Hocko To: Matthew Wilcox Cc: dsterba@suse.cz, Joe Perches , Waiman Long , Andrew Morton , David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Linus Torvalds , David Rientjes , Johannes Weiner , Dan Carpenter , "Jason A . Donenfeld" , linux-mm@kvack.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, linux-pm@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-amlogic@lists.infradead.org, linux-mediatek@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-ppp@vger.kernel.org, wireguard@lists.zx2c4.com, linux-wireless@vger.kernel.org, devel@driverdev.osuosl.org, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-fscrypt@vger.kernel.org, ecryptfs@vger.kernel.org, kasan-dev@googlegroups.com, linux-bluetooth@vger.kernel.org, linux-wpan@vger.kernel.org, linux-sctp@vger.kernel.org, linux-nfs@vger.kernel.org, tipc-discussion@lists.sourceforge.net, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org Subject: Re: [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive() Message-ID: <20200617125553.GO9499@dhcp22.suse.cz> References: <20200616015718.7812-1-longman@redhat.com> <20200616230130.GJ27795@twin.jikos.cz> <20200617003711.GD8681@bombadil.infradead.org> <20200617071212.GJ9499@dhcp22.suse.cz> <20200617110820.GG8681@bombadil.infradead.org> <20200617113157.GM9499@dhcp22.suse.cz> <20200617122321.GJ8681@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200617122321.GJ8681@bombadil.infradead.org> X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.30rc1 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" On Wed 17-06-20 05:23:21, Matthew Wilcox wrote: > On Wed, Jun 17, 2020 at 01:31:57PM +0200, Michal Hocko wrote: > > On Wed 17-06-20 04:08:20, Matthew Wilcox wrote: > > > If you call vfree() under > > > a spinlock, you're in trouble. in_atomic() only knows if we hold a > > > spinlock for CONFIG_PREEMPT, so it's not safe to check for in_atomic() > > > in __vfree(). So we need the warning in order that preempt people can > > > tell those without that there is a bug here. > > > > ... Unless I am missing something in_interrupt depends on preempt_count() as > > well so neither of the two is reliable without PREEMPT_COUNT configured. > > preempt_count() always tracks whether we're in interrupt context, > regardless of CONFIG_PREEMPT. The difference is that CONFIG_PREEMPT > will track spinlock acquisitions as well. Right you are! Thanks for the clarification. I find the situation around preempt_count quite confusing TBH. Looking at existing users of in_atomic() (e.g. a random one zd_usb_iowrite16v_async which check in_atomic and then does GFP_KERNEL allocation which would be obviously broken on !PREEMPT if the function can be called from an atomic context), I am wondering whether it would make sense to track atomic context also for !PREEMPT. This check is just terribly error prone. -- Michal Hocko SUSE Labs