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=-4.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 3256EC433E6 for ; Fri, 28 Aug 2020 19:24:54 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 7F18A20848 for ; Fri, 28 Aug 2020 19:24:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cbl6o1Iv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F18A20848 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-19711-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 24536 invoked by uid 550); 28 Aug 2020 19:24:45 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 24514 invoked from network); 28 Aug 2020 19:24:44 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1598642671; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=sg9fSrFQWXxpehnV4M1dhnTgmup13p6OKz0M6A4ji4k=; b=cbl6o1Ivu+iE/vpNZM5sziUiybyqNX1mY+WKWDVIxnrvFIxBC5DJgbqXIYoNMaTM2wKX2E ZJFvSOwESJ/jdaqvv0AYTIdQ817RuF6yeom57l/WvsSBBWx37nAZyNNLvgr640BAtL25sh 4xz3VL8po58gYvCFG8DHjDkVKwVYdzs= X-MC-Unique: w0KKgvflMN6fGsKM0dzwlw-1 Date: Fri, 28 Aug 2020 14:24:13 -0500 From: Josh Poimboeuf To: Miroslav Benes Cc: Kristen Carlson Accardi , Kees Cook , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, arjan@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, live-patching@vger.kernel.org, Hongjiu Lu , joe.lawrence@redhat.com Subject: Re: [PATCH v4 00/10] Function Granular KASLR Message-ID: <20200828192413.p6rctr42xtuh2c2e@treble> References: <20200717170008.5949-1-kristen@linux.intel.com> <202007220738.72F26D2480@keescook> <20200722160730.cfhcj4eisglnzolr@treble> <202007221241.EBC2215A@keescook> <301c7fb7d22ad6ef97856b421873e32c2239d412.camel@linux.intel.com> <20200722213313.aetl3h5rkub6ktmw@treble> <46c49dec078cb8625a9c3a3cd1310a4de7ec760b.camel@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 On Fri, Aug 28, 2020 at 12:21:13PM +0200, Miroslav Benes wrote: > > Hi there! I was trying to find a super easy way to address this, so I > > thought the best thing would be if there were a compiler or linker > > switch to just eliminate any duplicate symbols at compile time for > > vmlinux. I filed this question on the binutils bugzilla looking to see > > if there were existing flags that might do this, but H.J. Lu went ahead > > and created a new one "-z unique", that seems to do what we would need > > it to do. > > > > https://sourceware.org/bugzilla/show_bug.cgi?id=26391 > > > > When I use this option, it renames any duplicate symbols with an > > extension - for example duplicatefunc.1 or duplicatefunc.2. You could > > either match on the full unique name of the specific binary you are > > trying to patch, or you match the base name and use the extension to > > determine original position. Do you think this solution would work? > > Yes, I think so (thanks, Joe, for testing!). > > It looks cleaner to me than the options above, but it may just be a matter > of taste. Anyway, I'd go with full name matching, because -z unique-symbol > would allow us to remove sympos altogether, which is appealing. > > > If > > so, I can modify livepatch to refuse to patch on duplicated symbols if > > CONFIG_FG_KASLR and when this option is merged into the tool chain I > > can add it to KBUILD_LDFLAGS when CONFIG_FG_KASLR and livepatching > > should work in all cases. > > Ok. > > Josh, Petr, would this work for you too? Sounds good to me. Kristen, thanks for finding a solution! -- Josh