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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, 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 87EC9C54FCF for ; Mon, 20 Apr 2020 19:01:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 669712084D for ; Mon, 20 Apr 2020 19:01:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="L6nXO9t8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726910AbgDTTBv (ORCPT ); Mon, 20 Apr 2020 15:01:51 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:60042 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726017AbgDTTBu (ORCPT ); Mon, 20 Apr 2020 15:01:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587409308; 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=TSLwQrrbB4jA9+xtPLBleNLhnBPRnJn4gzcm+9Y3LWI=; b=L6nXO9t8duVWqGb8KKqzoo4cdnQdFH1wrggt+5ycabTebFPez9MkpZrSubXLluD9bjzyYb VBu7RHAzBwDhDz6cEf/rRvt6xIlI2Vf9JBB7K4LJFVUFV+DqiEDNi5GBCcgNygUu0FpNGY Bk0L6+jHMn3j7vw6Fj9CXUGWdNjQdfc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-61-H7H8GzLnOluoZ1D01wS8GA-1; Mon, 20 Apr 2020 15:01:45 -0400 X-MC-Unique: H7H8GzLnOluoZ1D01wS8GA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D3AD7801E5E; Mon, 20 Apr 2020 19:01:43 +0000 (UTC) Received: from redhat.com (ovpn-112-171.phx2.redhat.com [10.3.112.171]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 25F255C1B2; Mon, 20 Apr 2020 19:01:43 +0000 (UTC) Date: Mon, 20 Apr 2020 15:01:41 -0400 From: Joe Lawrence To: Josh Poimboeuf Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Jessica Yu Subject: Re: [PATCH v2 2/9] livepatch: Apply vmlinux-specific KLP relocations early Message-ID: <20200420190141.GB13807@redhat.com> References: <83eb0be61671eab05e2d7bcd0aa848f6e20087b0.1587131959.git.jpoimboe@redhat.com> <20200420175751.GA13807@redhat.com> <20200420182516.6awwwbvoen62gwbr@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200420182516.6awwwbvoen62gwbr@treble> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Mon, Apr 20, 2020 at 01:25:16PM -0500, Josh Poimboeuf wrote: > On Mon, Apr 20, 2020 at 01:57:51PM -0400, Joe Lawrence wrote: > > On Fri, Apr 17, 2020 at 09:04:27AM -0500, Josh Poimboeuf wrote: > > > > > > [ ... snip ... ] > > > > > > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c > > > index 40cfac8156fd..5fda3afc0285 100644 > > > --- a/kernel/livepatch/core.c > > > +++ b/kernel/livepatch/core.c > > > > > > [ ... snip ... ] > > > > > > +int klp_write_relocations(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, > > > + const char *shstrtab, const char *strtab, > > > + unsigned int symndx, struct module *pmod, > > > + const char *objname) > > > { > > > int i, cnt, ret = 0; > > > - const char *objname, *secname; > > > char sec_objname[MODULE_NAME_LEN]; > > > Elf_Shdr *sec; > > > > > > - if (WARN_ON(!klp_is_object_loaded(obj))) > > > - return -EINVAL; > > > - > > > - objname = klp_is_module(obj) ? obj->name : "vmlinux"; > > > - > > > /* For each klp relocation section */ > > > - for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) { > > > - sec = pmod->klp_info->sechdrs + i; > > > - secname = pmod->klp_info->secstrings + sec->sh_name; > > > + for (i = 1; i < ehdr->e_shnum; i++) { > > > + sec = sechdrs + i; > > > > Hi Josh, minor bug: > > > > Note the for loop through the section headers in > > klp_write_relocations(), but its calling function ... > > > > > [ ... snip ... ] > > > > > > diff --git a/kernel/module.c b/kernel/module.c > > > index 646f1e2330d2..d36ea8a8c3ec 100644 > > > --- a/kernel/module.c > > > +++ b/kernel/module.c > > > @@ -2334,11 +2334,12 @@ static int apply_relocations(struct module *mod, const struct load_info *info) > > > if (!(info->sechdrs[infosec].sh_flags & SHF_ALLOC)) > > > continue; > > > > > > - /* Livepatch relocation sections are applied by livepatch */ > > > if (info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH) > > > - continue; > > > - > > > - if (info->sechdrs[i].sh_type == SHT_REL) > > > + err = klp_write_relocations(info->hdr, info->sechdrs, > > > + info->secstrings, > > > + info->strtab, > > > + info->index.sym, mod, NULL); > > > + else if (info->sechdrs[i].sh_type == SHT_REL) > > > err = apply_relocate(info->sechdrs, info->strtab, > > > info->index.sym, i, mod); > > > else if (info->sechdrs[i].sh_type == SHT_RELA) > > > > ... apply_relocations() is also iterating over the section headers (the > > diff context doesn't show it here, but i is an incrementing index over > > sechdrs[]). > > > > So if there is more than one KLP relocation section, we'll process them > > multiple times. At least the x86 relocation code will detect this and > > fail the module load with an invalid relocation (existing value not > > zero). > > Ah, yes, good catch! > The same test case passed with a small modification to push the foreach KLP section part to a kernel/livepatch/core.c local function and exposing the klp_resolve_symbols() + apply_relocate_add() for a given section to kernel/module.c. Something like following... -- Joe -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 8b6886c2d5c7..516f285ccc82 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -232,9 +232,9 @@ void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor); struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id); struct klp_state *klp_get_prev_state(unsigned long id); -int klp_write_relocations(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, - const char *shstrtab, const char *strtab, - unsigned int symindex, struct module *pmod, +int klp_write_relocations(Elf_Shdr *sechdrs, const char *shstrtab, + const char *strtab, unsigned int symndx, + unsigned int relsec, struct module *pmod, const char *objname); /* Used to annotate symbol relocations in livepatches */ diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index d2610f63e70b..d74fd7d10f16 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -285,14 +285,48 @@ static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab, * the to-be-patched module to be loaded and patched sometime *after* the * klp module is loaded. */ -int klp_write_relocations(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, - const char *shstrtab, const char *strtab, - unsigned int symndx, struct module *pmod, + +int klp_write_relocations(Elf_Shdr *sechdrs, const char *shstrtab, + const char *strtab, unsigned int symndx, + unsigned int relsec, struct module *pmod, const char *objname) { - int i, cnt, ret = 0; char sec_objname[MODULE_NAME_LEN]; Elf_Shdr *sec; + int cnt, ret; + + sec = sechdrs + relsec; + + /* + * Format: .klp.rela.sec_objname.section_name + * See comment in klp_resolve_symbols() for an explanation + * of the selected field width value. + */ + cnt = sscanf(shstrtab + sec->sh_name, KLP_RELA_PREFIX "%55[^.]", + sec_objname); + if (cnt != 1) { + pr_err("section %s has an incorrectly formatted name\n", + shstrtab + sec->sh_name); + return -EINVAL; + } + + if (strcmp(objname ? objname : "vmlinux", sec_objname)) + return 0; + + ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname); + if (ret) + return ret; + + return apply_relocate_add(sechdrs, strtab, symndx, relsec, pmod); +} + +static int klp_write_all_relocations(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, + const char *shstrtab, const char *strtab, + unsigned int symndx, struct module *pmod, + const char *objname) +{ + int i, ret; + Elf_Shdr *sec; /* For each klp relocation section */ for (i = 1; i < ehdr->e_shnum; i++) { @@ -300,34 +334,13 @@ int klp_write_relocations(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, if (!(sec->sh_flags & SHF_RELA_LIVEPATCH)) continue; - /* - * Format: .klp.rela.sec_objname.section_name - * See comment in klp_resolve_symbols() for an explanation - * of the selected field width value. - */ - cnt = sscanf(shstrtab + sec->sh_name, KLP_RELA_PREFIX "%55[^.]", - sec_objname); - if (cnt != 1) { - pr_err("section %s has an incorrectly formatted name\n", - shstrtab + sec->sh_name); - ret = -EINVAL; - break; - } - - if (strcmp(objname ? objname : "vmlinux", sec_objname)) - continue; - - ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, - sec_objname); + ret = klp_write_relocations(sechdrs, shstrtab, strtab, symndx, + i, pmod, objname); if (ret) - break; - - ret = apply_relocate_add(sechdrs, strtab, symndx, i, pmod); - if (ret) - break; + return ret; } - return ret; + return 0; } /* @@ -773,11 +786,11 @@ static int klp_init_object_loaded(struct klp_patch *patch, * written earlier during the initialization of the klp module * itself. */ - ret = klp_write_relocations(&info->hdr, info->sechdrs, - info->secstrings, - patch->mod->core_kallsyms.strtab, - info->symndx, patch->mod, - obj->name); + ret = klp_write_all_relocations(&info->hdr, info->sechdrs, + info->secstrings, + patch->mod->core_kallsyms.strtab, + info->symndx, patch->mod, + obj->name); if (ret) return ret; } diff --git a/kernel/module.c b/kernel/module.c index 86736e2ff73d..04e5f5d55eb4 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2322,10 +2322,11 @@ static int apply_relocations(struct module *mod, const struct load_info *info) continue; if (info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH) - err = klp_write_relocations(info->hdr, info->sechdrs, + err = klp_write_relocations(info->sechdrs, info->secstrings, info->strtab, - info->index.sym, mod, NULL); + info->index.sym, i, mod, + NULL); else if (info->sechdrs[i].sh_type == SHT_REL) err = apply_relocate(info->sechdrs, info->strtab, info->index.sym, i, mod);