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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 5FFDCC2D0B1 for ; Thu, 6 Feb 2020 12:42:07 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id AEBE120661 for ; Thu, 6 Feb 2020 12:42:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="gqic0Va6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AEBE120661 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17706-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 5250 invoked by uid 550); 6 Feb 2020 12:42:01 -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 5230 invoked from network); 6 Feb 2020 12:42:00 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=R/G+XnWKaWnsAGyAhnss7hjHPbcbIWyeMj56v/dBiw0=; b=gqic0Va6FFKhVWe+HoLEbDIOLX9fEBKJIGhNNTuJohRE1KWTHzScoZSh5QZns/Kn5b hBttK0s+AxHa4qxZpeGwOp2hnd64Kn9Qccdt5cPeKT6TueBKOUw7Vph0IjYTTpvC8Jhk Y4/xNY2FQH3hPvZCiYOUSgf8lU6mukHJaE3SU= 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=R/G+XnWKaWnsAGyAhnss7hjHPbcbIWyeMj56v/dBiw0=; b=XRrTP3tLyNR1u34YzPKxo1XXWRRlXtLMiWxRCPnUhlqPH6nxOlPTa50Sg0on0dpr9m 6OBUTgda8+0bXeV6VVusZQGfZebJch0eN0fIo3lBF7W/Pnu/AIgaX3r2I6RVc5rtWk0M j8KB5QqbETxBplKwqS5Q83aXawlZDmXUKkLPQ0xbmc+taHKptSwdTW0zT9gHVzM43JBF NLIIBx7dUcsHX/ysj4GMXwbA6o3ZORXtpZ1sT/1jYI80bfQyEye1axJ68mzrnuycT8Jv YAj/Y/GfMezxFMaYcqUwIoBc3qsAh42O/0sAOnv2YvDDbTlC7hj8VROJbVEYMdPI6Ere ln1Q== X-Gm-Message-State: APjAAAW/9E4IInBKqGi1Nb+Hnel4uLp9YKgOxuxCt4I+CT35RvLBYHr9 O+p6HnPPkdK3FSdbkRO89fTWVA== X-Google-Smtp-Source: APXvYqzs3PSh1ujSf22dbd43fPKu0mlRTU+Ugms/ZlDsQaRqF7aFIOl1+GVNwH5FnEboLgfvMDiWsw== X-Received: by 2002:a9d:6457:: with SMTP id m23mr8928122otl.162.1580992908944; Thu, 06 Feb 2020 04:41:48 -0800 (PST) Date: Thu, 6 Feb 2020 04:41:46 -0800 From: Kees Cook To: Kristen Carlson Accardi Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, arjan@linux.intel.com, rick.p.edgecombe@intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, Jessica Yu Subject: Re: [RFC PATCH 10/11] module: Reorder functions Message-ID: <202002060440.E7ED91B@keescook> References: <20200205223950.1212394-1-kristen@linux.intel.com> <20200205223950.1212394-11-kristen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200205223950.1212394-11-kristen@linux.intel.com> On Wed, Feb 05, 2020 at 02:39:49PM -0800, Kristen Carlson Accardi wrote: > If a module has functions split out into separate text sections > (i.e. compiled with the -ffunction-sections flag), reorder the > functions to provide some code diversification to modules. > > Signed-off-by: Kristen Carlson Accardi Probably a good idea to add Jessica to CC in next version: Jessica Yu Reviewed-by: Kees Cook -Kees > --- > kernel/module.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 85 insertions(+) > > diff --git a/kernel/module.c b/kernel/module.c > index b56f3224b161..231563e95e61 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -53,6 +53,8 @@ > #include > #include > #include > +#include > +#include > #include > #include "module-internal.h" > > @@ -3245,6 +3247,87 @@ static int find_module_sections(struct module *mod, struct load_info *info) > return 0; > } > > +/* > + * shuffle_text_list() > + * Use a Fisher Yates algorithm to shuffle a list of text sections. > + */ > +static void shuffle_text_list(Elf_Shdr **list, int size) > +{ > + int i; > + unsigned int j; > + Elf_Shdr *temp; > + > + for (i = size - 1; i > 0; i--) { > + /* > + * TBD - seed. We need to be able to use a known > + * seed so that we can non-randomly randomize for > + * debugging. > + */ > + > + // pick a random index from 0 to i > + get_random_bytes(&j, sizeof(j)); > + j = j % (i + 1); > + > + temp = list[i]; > + list[i] = list[j]; > + list[j] = temp; > + } > +} > + > +/* > + * randomize_text() > + * Look through the core section looking for executable code sections. > + * Store sections in an array and then shuffle the sections > + * to reorder the functions. > + */ > +static void randomize_text(struct module *mod, struct load_info *info) > +{ > + int i; > + int num_text_sections = 0; > + Elf_Shdr **text_list; > + int size = 0; > + int max_sections = info->hdr->e_shnum; > + unsigned int sec = find_sec(info, ".text"); > + > + if (!IS_ENABLED(CONFIG_FG_KASLR) || !kaslr_enabled()) > + return; > + > + if (sec == 0) > + return; > + > + text_list = kmalloc_array(max_sections, sizeof(*text_list), GFP_KERNEL); > + if (text_list == NULL) > + return; > + > + for (i = 0; i < max_sections; i++) { > + Elf_Shdr *shdr = &info->sechdrs[i]; > + const char *sname = info->secstrings + shdr->sh_name; > + > + if (!(shdr->sh_flags & SHF_ALLOC) || > + !(shdr->sh_flags & SHF_EXECINSTR) || > + strstarts(sname, ".init")) > + continue; > + > + text_list[num_text_sections] = shdr; > + num_text_sections++; > + } > + > + shuffle_text_list(text_list, num_text_sections); > + > + for (i = 0; i < num_text_sections; i++) { > + Elf_Shdr *shdr = text_list[i]; > + unsigned int infosec; > + const char *sname; > + > + sname = info->secstrings + shdr->sh_name; > + infosec = shdr->sh_info; > + > + shdr->sh_entsize = get_offset(mod, &size, shdr, infosec); > + } > + > + kfree(text_list); > +} > + > static int move_module(struct module *mod, struct load_info *info) > { > int i; > @@ -3282,6 +3365,8 @@ static int move_module(struct module *mod, struct load_info *info) > } else > mod->init_layout.base = NULL; > > + randomize_text(mod, info); > + > /* Transfer each section which specifies SHF_ALLOC */ > pr_debug("final section addresses:\n"); > for (i = 0; i < info->hdr->e_shnum; i++) { > -- > 2.24.1 > -- Kees Cook