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 CB82ECDB47E for ; Wed, 18 Oct 2023 19:14:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231443AbjJRTON (ORCPT ); Wed, 18 Oct 2023 15:14:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58650 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229688AbjJRTOL (ORCPT ); Wed, 18 Oct 2023 15:14:11 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C023CAB; Wed, 18 Oct 2023 12:14:09 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1C838C433C7; Wed, 18 Oct 2023 19:14:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697656449; bh=dFRqduN7YTqHc7HQ6JGA9+8GGHtLEMQGa5F7wvBiPHc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ERr6Rza2enKVLtJLaYvNUvT3qymcYtjkxskJfJNvUezR7q5EiZujK8LY2HXB9L00Q 9kqYQTYAYz5hb+otyknNMAizUtiHBKDOUK/x0MxPaS7/nwv+/pxMUHXDM45wsOhzWv ab6/CY7i45HGx4N0ZAERFxvasZJi/k8FQr4/ilHv7oavWDqb1FRLBq2P9iEu9j3t01 ihYJYtIgLy+WKR5WDXxFYqVtCzzbZAnOwtszI2xVGMyGQejLhKOYNUV3aI3dHTiAfY 0LrcNQXUhB+v1ZcR01rZka5Bz5BgbN8o7UWl/l9n3T4hKenAjBHvg104KR3Fn2PENu 4nUHyDrZhi7uQ== Date: Wed, 18 Oct 2023 12:14:07 -0700 From: Josh Poimboeuf To: Borislav Petkov Cc: Ingo Molnar , linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, David Kaplan , "Peter Zijlstra (Intel)" , x86@kernel.org, David Howells Subject: Re: [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't used at runtime Message-ID: <20231018191407.n4ys6vefbio7z3sn@treble> References: <169713303534.3135.10558074245117750218.tip-bot2@tip-bot2> <20231018132352.GBZS/caGJ8Wk9kmTbg@fat_crate.local> <20231018151245.GCZS/17QhDGe7q6K+w@fat_crate.local> <20231018155433.z4auwckr5s27wnig@treble> <20231018175531.GEZTAcE2p92U1AuVp1@fat_crate.local> <20231018181431.skre6i6vzrxsprck@treble> <20231018182223.GFZTAiX4BJ6FT8bHzz@fat_crate.local> <20231018183915.xwamzzqjf6gehaou@treble> <20231018184431.GGZTAnj8V/R54S5KK9@fat_crate.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231018184431.GGZTAnj8V/R54S5KK9@fat_crate.local> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 18, 2023 at 08:44:31PM +0200, Borislav Petkov wrote: > On Wed, Oct 18, 2023 at 11:39:15AM -0700, Josh Poimboeuf wrote: > > And see my reply to that? Not trying to be daft, I just didn't see how > > your reply was responsive. > > > > A single WARN_ONCE() has the benefit of not overflowing dmesg, while > > also making the warning available to those looking at dmesg (or the > > taint flag), as those who care should be. > > A single WARN once is not enough as this is security-sensitive. Warns do > get ignored. > > > A rate-limited WARN() is problematic, as it overflows dmesg (and > > possibly wrapping other logs), potentially obscuring other important > > data. > > This will hopefully make people look by screaming louder. But no > guarantee. Not saying it is the right thing. > > UDing without any output is not the right thing either. > > All I'm saying is, there's no good solution for how to catch this and > make people report it. > > Make more sense? There are a lot of warnings which could become security concerns. By definition, a warning means something is seriously wrong. If it's ignored, all bets are off. That's why we taint the kernel. -- Josh